path: root/docs/en/xml/customization.xml

<!-- <!DOCTYPE appendix PUBLIC "-//OASIS//DTD DocBook V4.1//EN"> -->
<chapter id="customization">
  <title>Customising Bugzilla</title>

  <section id="cust-templates">
    <title>Template Customization</title>
    
    <para>
      Administrators can configure the look and feel of Bugzilla without
      having to edit Perl files or face the nightmare of massive merge
      conflicts when they upgrade to a newer version in the future.
    </para>
    
    <para>
      Templatization also makes localized versions of Bugzilla possible, 
      for the first time. It's possible to have Bugzilla's UI language 
      determined by the user's browser. More information is available in
      <xref linkend="template-http-accept"/>.
    </para>
    
    <section id="template-directory">
      <title>Template Directory Structure</title>
      <para>
        The template directory structure starts with top level directory 
        named <filename>template</filename>, which contains a directory
        for each installed localization. The next level defines the
        language used in the templates. Bugzilla comes with English
        templates, so the directory name is <filename>en</filename>,
        and we will discuss <filename>template/en</filename> throughout
        the documentation. Below <filename>template/en</filename> is the
        <filename>default</filename> directory, which contains all the
        standard templates shipped with Bugzilla.
      </para>

      <warning>
        <para>
          A directory <filename>data/templates</filename> also exists;
          this is where Template Toolkit puts the compiled versions of
          the templates from either the default or custom directories.
          <emphasis>Do not</emphasis> directly edit the files in this
          directory, or all your changes will be lost the next time
          Template Toolkit recompiles the templates.
        </para>
      </warning>
    </section>

    <section id="template-method">
      <title>Choosing a Customization Method</title>
      <para>
        If you want to edit Bugzilla's templates, the first decision
        you must make is how you want to go about doing so. There are two
        choices, and which you use depends mainly on the scope of your 
        modifications, and the method you plan to use to upgrade Bugzilla.
      </para> 

      <para>
        The first method of making customizations is to directly edit the
        templates found in <filename>template/en/default</filename>.
        This is probably the best way to go about it if you are going to
        be upgrading Bugzilla through CVS, because if you then execute
        a <command>cvs update</command>, any changes you have made will
        be merged automagically with the updated versions.
      </para>

      <note>
        <para>
          If you use this method, and CVS conflicts occur during an
          update, the conflicted templates (and possibly other parts
          of your installation) will not work until they are resolved.
        </para>
      </note>

      <para>
        The second method is to copy the templates to be modified
        into a mirrored directory structure under 
        <filename>template/en/custom</filename>. Templates in this
        directory structure automatically override any identically-named
        and identically-located templates in the 
        <filename>default</filename> directory. 
      </para>

      <note>
        <para>
          The <filename>custom</filename> directory does not exist
          at first and must be created if you want to use it.
        </para>
      </note>

      <para>
        The second method of customization should be used if you 
        use the overwriting method of upgrade, because otherwise 
        your changes will be lost.  This method may also be better if
        you are using the CVS method of upgrading and are going to make major
        changes, because it is guaranteed that the contents of this directory
        will not be touched during an upgrade, and you can then decide whether
        to continue using your own templates, or make the effort to merge your
        changes into the new versions by hand.
      </para>

      <para>
        Using this method, your installation may break if incompatible
        changes are made to the template interface.  Such changes should
        be documented in the release notes, provided you are using a
        stable release of Bugzilla.  If you use using unstable code, you will
        need to deal with this one yourself, although if possible the changes
        will be mentioned before they occur in the deprecations section of the
        previous stable release's release notes.
      </para>

      <note>
        <para>
          Regardless of which method you choose, it is recommended that
          you run <command>./checksetup.pl</command> after creating or
          editing any templates in the <filename>template/en/default</filename>
          directory, and after editing any templates in the 
          <filename>custom</filename> directory.
        </para>
      </note>

      <warning>
        <para>
          It is <emphasis>required</emphasis> that you run 
          <command>./checksetup.pl</command> after creating a new
          template in the <filename>custom</filename> directory. Failure
          to do so will raise an incomprehensible error message.
        </para>
      </warning>
    </section>
    
    <section id="template-edit">
      <title>How To Edit Templates</title>
      
      <note>
        <para>
          If you are making template changes that you intend on submitting back
          for inclusion in standard Bugzilla, you should read the relevant
          sections of the 
          <ulink url="http://www.bugzilla.org/docs/developer.html">Developers'
          Guide</ulink>.
        </para>
      </note>
      
      <para>
        The syntax of the Template Toolkit language is beyond the scope of
        this guide. It's reasonably easy to pick up by looking at the current 
        templates; or, you can read the manual, available on the
        <ulink url="http://www.template-toolkit.org">Template Toolkit home
        page</ulink>.
      </para>
      
      <para>
        One thing you should take particular care about is the need
        to properly HTML filter data that has been passed into the template.
        This means that if the data can possibly contain special HTML characters
        such as &lt;, and the data was not intended to be HTML, they need to be
        converted to entity form, i.e. &amp;lt;.  You use the 'html' filter in the
        Template Toolkit to do this.  If you forget, you may open up
        your installation to cross-site scripting attacks.
      </para>

      <para>
        Also note that Bugzilla adds a few filters of its own, that are not
        in standard Template Toolkit.  In particular, the 'url_quote' filter
        can convert characters that are illegal or have special meaning in URLs,
        such as &amp;, to the encoded form, i.e. %26.  This actually encodes most
        characters (but not the common ones such as letters and numbers and so
        on), including the HTML-special characters, so there's never a need to
        HTML filter afterwards.
      </para>
 
      <para>
        Editing templates is a good way of doing a <quote>poor man's custom
        fields</quote>.
        For example, if you don't use the Status Whiteboard, but want to have
        a free-form text entry box for <quote>Build Identifier</quote>,
        then you can just
        edit the templates to change the field labels. It's still be called
        status_whiteboard internally, but your users don't need to know that.
      </para>
      
    </section>
            
    
    <section id="template-formats">
      <title>Template Formats and Types</title>
      
      <para>
        Some CGI's have the ability to use more than one template. For example,
        <filename>buglist.cgi</filename> can output itself as RDF, or as two 
        formats of HTML (complex and simple). The mechanism that provides this 
        feature is extensible.
      </para>

      <para>
        Bugzilla can support different types of output, which again can have 
        multiple formats. In order to request a certain type, you can append 
        the &amp;ctype=&lt;contenttype&gt; (such as rdf or html) to the 
        <filename>&lt;cginame&gt;.cgi</filename> URL. If you would like to 
        retrieve a certain format, you can use the &amp;format=&lt;format&gt; 
        (such as simple or complex) in the URL.
      </para>
      
      <para>
        To see if a CGI supports multiple output formats and types, grep the
        CGI for <quote>get_format</quote>. If it's not present, adding
        multiple format/type support isn't too hard - see how it's done in
        other CGIs, e.g. config.cgi.
      </para>
      
      <para>
        To make a new format template for a CGI which supports this, 
        open a current template for
        that CGI and take note of the INTERFACE comment (if present.) This 
        comment defines what variables are passed into this template. If 
        there isn't one, I'm afraid you'll have to read the template and
        the code to find out what information you get. 
      </para>     
  
      <para>
        Write your template in whatever markup or text style is appropriate.
      </para>
      
      <para>
        You now need to decide what content type you want your template
        served as. The content types are defined in the
        <filename>Bugzilla/Constants.pm</filename> file in the 
        <filename>contenttypes</filename>
        constant. If your content type is not there, add it. Remember
        the three- or four-letter tag assigned to your content type. 
        This tag will be part of the template filename.
      </para>

      <note>
        <para>
          After adding or changing a content type, it's suitable to edit
          <filename>Bugzilla/Constants.pm</filename> in order to reflect
          the changes. Also, the file should be kept up to date after an
          upgrade if content types have been customized in the past. 
        </para>
      </note>
      
      <para>
        Save the template as <filename>&lt;stubname&gt;-&lt;formatname&gt;.&lt;contenttypetag&gt;.tmpl</filename>. 
        Try out the template by calling the CGI as 
        <filename>&lt;cginame&gt;.cgi?format=&lt;formatname&gt;&amp;ctype=&lt;type&gt;</filename> .
      </para>       
    </section>
    
    
    <section id="template-specific">
      <title>Particular Templates</title>
      
      <para>
        There are a few templates you may be particularly interested in
        customizing for your installation.
      </para>
      
      <para>
        <command>index.html.tmpl</command>:
        This is the Bugzilla front page.
      </para>      

      <para>
        <command>global/header.html.tmpl</command>:
        This defines the header that goes on all Bugzilla pages.
        The header includes the banner, which is what appears to users
        and is probably what you want to edit instead.  However the
        header also includes the HTML HEAD section, so you could for
        example add a stylesheet or META tag by editing the header.
      </para>

      <para>
        <command>global/banner.html.tmpl</command>:
        This contains the <quote>banner</quote>, the part of the header
        that appears
        at the top of all Bugzilla pages.  The default banner is reasonably
        barren, so you'll probably want to customize this to give your
        installation a distinctive look and feel.  It is recommended you
        preserve the Bugzilla version number in some form so the version 
        you are running can be determined, and users know what docs to read.
      </para>

      <para>
        <command>global/footer.html.tmpl</command>:
        This defines the footer that goes on all Bugzilla pages.  Editing
        this is another way to quickly get a distinctive look and feel for
        your Bugzilla installation.
      </para>

      <para>
        <command>global/variables.none.tmpl</command>:
        This defines a list of terms that may be changed in order to
        <quote>brand</quote> the Bugzilla instance In this way, terms
        like <quote>bugs</quote> can be replaced with <quote>issues</quote>
        across the whole Bugzilla installation. The name
        <quote>Bugzilla</quote> and other words can be customized as well.
      </para>

      <para>
        <command>list/table.html.tmpl</command>:
        This template controls the appearance of the bug lists created
        by Bugzilla. Editing this template allows per-column control of 
        the width and title of a column, the maximum display length of
        each entry, and the wrap behaviour of long entries.
        For long bug lists, Bugzilla inserts a 'break' every 100 bugs by
        default; this behaviour is also controlled by this template, and
        that value can be modified here.
       </para>

      <para>
        <command>bug/create/user-message.html.tmpl</command>:
        This is a message that appears near the top of the bug reporting page.
        By modifying this, you can tell your users how they should report
        bugs.
      </para>

      <para>
        <command>bug/process/midair.html.tmpl</command>:
        This is the page used if two people submit simultaneous changes to the
        same bug.  The second person to submit their changes will get this page
        to tell them what the first person did, and ask if they wish to
        overwrite those changes or go back and revisit the bug.  The default
        title and header on this page read "Mid-air collision detected!"  If
        you work in the aviation industry, or other environment where this
        might be found offensive (yes, we have true stories of this happening)
        you'll want to change this to something more appropriate for your
        environment.
      </para>

      <para>
        <command>bug/create/create.html.tmpl</command> and
        <command>bug/create/comment.txt.tmpl</command>:
        You may not wish to go to the effort of creating custom fields in
        Bugzilla, yet you want to make sure that each bug report contains
        a number of pieces of important information for which there is not
        a special field. The bug entry system has been designed in an
        extensible fashion to enable you to add arbitrary HTML widgets,
        such as drop-down lists or textboxes, to the bug entry page
        and have their values appear formatted in the initial comment.
        A hidden field that indicates the format should be added inside
        the form in order to make the template functional. Its value should
        be the suffix of the template filename. For example, if the file
        is called <filename>create-cust.html.tmpl</filename>, then
        <programlisting>&lt;input type="hidden" name="format" value="cust"&gt;</programlisting>
        should be used inside the form.
      </para>

      <para>  
        An example of this is the mozilla.org 
        <ulink url="http://landfill.bugzilla.org/bugzilla-tip/enter_bug.cgi?product=WorldControl&amp;format=guided">guided 
        bug submission form</ulink>. The code for this comes with the Bugzilla
        distribution as an example for you to copy. It can be found in the
        files 
        <filename>create-guided.html.tmpl</filename> and
        <filename>comment-guided.html.tmpl</filename>.
      </para>  

      <para>
        So to use this feature, create a custom template for 
        <filename>enter_bug.cgi</filename>. The default template, on which you
        could base it, is 
        <filename>custom/bug/create/create.html.tmpl</filename>.
        Call it <filename>create-&lt;formatname&gt;.html.tmpl</filename>, and
        in it, add widgets for each piece of information you'd like
        collected - such as a build number, or set of steps to reproduce.
      </para>

      <para>
        Then, create a template like 
        <filename>custom/bug/create/comment.txt.tmpl</filename>, and call it 
        <filename>comment-&lt;formatname&gt;.txt.tmpl</filename>. This 
        template should reference the form fields you have created using
        the syntax <filename>[% form.&lt;fieldname&gt; %]</filename>. When a 
        bug report is
        submitted, the initial comment attached to the bug report will be
        formatted according to the layout of this template.
      </para> 

      <para>
        For example, if your custom enter_bug template had a field
        <programlisting>&lt;input type="text" name="buildid" size="30"&gt;</programlisting>
        and then your comment.txt.tmpl had
        <programlisting>BuildID: [% form.buildid %]</programlisting>
        then something like
        <programlisting>BuildID: 20020303</programlisting>
        would appear in the initial comment.
      </para>            
    </section>          


    <section id="template-http-accept">
      <title>Configuring Bugzilla to Detect the User's Language</title>

      <para>Bugzilla honours the user's Accept: HTTP header. You can install
      templates in other languages, and Bugzilla will pick the most appropriate
      according to a priority order defined by you. Many
      language templates can be obtained from <ulink 
      url="http://www.bugzilla.org/download.html#localizations"/>. Instructions
      for submitting new languages are also available from that location.
      </para>

      <para>After untarring the localizations (or creating your own) in the 
      <filename class="directory">BUGZILLA_ROOT/template</filename> directory,
      you must update the <option>languages</option> parameter to contain any
      localizations you'd like to permit. You may also wish to set the
      <option>defaultlanguage</option> parameter to something other than
      <quote>en</quote> if you don't want English to be the default language.
      </para>
    </section>
      
  </section>

  <section id="cust-hooks">
    <title>The Bugzilla Extension Mechanism</title>
        
    <warning>
      <para>
        Custom extensions require Template Toolkit version 2.12 or
        above, or the application of a patch.  See <ulink
        url="http://bugzilla.mozilla.org/show_bug.cgi?id=239112">bug
        239112</ulink> for details.
      </para>
    </warning>
       
    <para>
      Extensions are a way for extensions to Bugzilla to insert code
      into the standard Bugzilla templates and source files
      without modifying these files themselves.  The extension mechanism 
      defines a consistent API for extending the standard templates and source files 
      in a way that cleanly separates standard code from extension code.  
      Hooks reduce merge conflicts and make it easier to write extensions that work 
      across multiple versions of Bugzilla, making upgrading a Bugzilla installation 
      with installed extensions easier. Furthermore, they make it easy to install 
      and remove extensions as each extension is nothing more than a 
      simple directory structure. 
    </para>
    
    <para>
      There are two main types of hooks: code hooks and template hooks. Code 
      hooks allow extensions to invoke code at specific points in various 
      source files, while template hooks allow extensions to add elements to 
      the Bugzilla user interface. 
    </para>

    <para>
      A hook is just a named place in a standard source or template file
      where extension source code or template files for that hook get processed. 
      Each extension has a corresponding directory in the Bugzilla directory 
      tree (<filename>BUGZILLA_ROOT/extensions/extension_name</filename>).  Hooking 
      an extension source file or template to a hook is as simple as putting 
      the extension file into extension's template or code directory. 
      When Bugzilla processes the source file or template and reaches the hook, 
      it will process all extension files in the hook's directory. 
      The hooks themselves can be added into any source file or standard template 
      upon request by extension authors.
    </para>
    
    <para>
      To use hooks to extend Bugzilla, first make sure there is
      a hook at the appropriate place within the source file or template you 
      want to extend. The exact appearence of a hook depends on if the hook 
      is a code hook or a template hook. 
    </para>
    
    <para>
      Code hooks appear in Bugzilla source files as a single method call 
      in the format <literal role="code">Bugzilla::Hook->process("<varname>name</varname>");</literal>.
      for instance, <filename>enter_bug.cgi</filename> may invoke the hook 
      "<varname>enter_bug-defaultvars</varname>". Thus, a source file at 
      <filename>BUGZILLA_ROOT/extensions/EXTENSION_NAME/code/enter_bug-entrydefaultvars.pl</filename>
      will be automatically invoked when the code hook is reached. 
    </para>
   
    <para>  
      Template hooks appear in the standard Bugzilla templates as a 
      single directive in the format
      <literal role="code">[% Hook.process("<varname>name</varname>") %]</literal>,
      where <varname>name</varname> is the unique name of the hook.
    </para>

    <para>
      If you aren't sure what you want to extend or just want to browse the 
      available hooks, either use your favorite multi-file search
      tool (e.g. <command>grep</command>) to search the standard templates
      for occurrences of <methodname>Hook.process</methodname> or the source 
      files for occurrences of <methodname>Bugzilla::Hook::process</methodname>.
    </para>

    <para>
      If there is no hook at the appropriate place within the Bugzilla 
      source file or template you want to extend,
      <ulink url="http://bugzilla.mozilla.org/enter_bug.cgi?product=Bugzilla&amp;component=User%20Interface">file
      a bug requesting one</ulink>, specifying:
    </para>

    <simplelist>
      <member>the source or template file for which you are 
          requesting a hook;</member>
      <member>
        where in the file you would like the hook to be placed
        (line number/position for latest version of the file in CVS
        or description of location);
      </member>
      <member>the purpose of the hook;</member>
      <member>a link to information about your extension, if any.</member>
    </simplelist>

    <para>
      The Bugzilla reviewers will promptly review each hook request,
      name the hook, add it to the template or source file, and check 
      the new version of the template into CVS.
    </para>

    <para>
      You may optionally attach a patch to the bug which implements the hook
      and check it in yourself after receiving approval from a Bugzilla
      reviewer.  The developers may suggest changes to the location of the
      hook based on their analysis of your needs or so the hook can satisfy
      the needs of multiple extensions, but the process of getting hooks
      approved and checked in is not as stringent as the process for general
      changes to Bugzilla, and any extension, whether released or still in
      development, can have hooks added to meet their needs.
    </para>

    <para>
      After making sure the hook you need exists (or getting it added if not),
      add your extension to the directory within the Bugzilla
      extensions tree corresponding to the hook. 
    </para>
    
    <para>
      That's it!  Now, when the source file or template containing the hook
      is processed, your extension file will be processed at the point 
      where the hook appears.
    </para>

    <para>
      For example, let's say you have an extension named Projman that adds
      project management capabilities to Bugzilla.  Projman has an
      administration interface <filename>edit-projects.cgi</filename>, 
      and you want to add a link to it into the navigation bar at the bottom
      of every Bugzilla page for those users who are authorized
      to administer projects.
    </para>

    <para>
      The navigation bar is generated by the template file
      <filename>useful-links.html.tmpl</filename>, which is located in
      the <filename>global/</filename> subdirectory on the standard Bugzilla 
      template path
      <filename>BUGZILLA_ROOT/template/en/default/</filename>.
      Looking in <filename>useful-links.html.tmpl</filename>, you find
      the following hook at the end of the list of standard Bugzilla
      administration links:
    </para>

    <programlisting><![CDATA[...
    [% ', <a href="editkeywords.cgi">keywords</a>' 
                                              IF user.groups.editkeywords %]
    [% Hook.process("edit") %]
...]]></programlisting>

    <para>
      The corresponding extension file for this hook is
      <filename>BUGZILLA_ROOT/extensions/projman/template/en/hook/global/useful-links-edit.html.tmpl</filename>.
      You then create that template file and add the following constant:
    </para>

    <programlisting><![CDATA[...[% ', <a href="edit-projects.cgi">projects</a>' IF user.groups.projman_admins %]]]></programlisting>

    <para>
      Voila!  The link now appears after the other administration links in the
      navigation bar for users in the <literal>projman_admins</literal> group.
    </para>
    
    <para>
      Now, let us say your extension adds a custom "project_manager" field 
      to enter_bug.cgi. You want to modify the CGI script to set the default 
      project manager to be productname@company.com. Looking at 
      <filename>enter_bug.cgi</filename>, you see the enter_bug-entrydefaultvars 
      hook near the bottom of the file before the default form values are set. 
      The corresponding extension source file for this hook is located at 
      <filename>BUGZILLA_ROOT/extensions/projman/code/enter_bug-entrydefaultvars.pl</filename>.
      You then create that file and add the following:
    </para>
    
    <programlisting>$default{'project_manager'} = $product.'@company.com';</programlisting>
    
    <para>
      This code will be invoked whenever enter_bug.cgi is executed. 
      Assuming that the rest of the customization was completed (e.g. the 
      custom field was added to the enter_bug template and the required hooks 
      were used in process_bug.cgi), the new field will now have this 
      default value. 
    </para>
      
    <para>
      Notes:
    </para>

    <itemizedlist>
      <listitem>
        <para>
          If your extension includes entirely new templates in addition to
          extensions of standard templates, it should store those new
          templates in its
          <filename>BUGZILLA_ROOT/extensions/template/en/</filename> 
          directory. Extension template directories, like the 
          <filename>default/</filename> and <filename>custom/</filename>
          directories, are part of the template search path, so putting templates
          there enables them to be found by the template processor.
        </para>

        <para>
          The template processor looks for templates first in the
          <filename>custom/</filename> directory (i.e. templates added by the 
          specific installation), then in the <filename>extensions/</filename>
          directory (i.e. templates added by extensions), and finally in the 
          <filename>default/</filename> directory (i.e. the standard Bugzilla 
          templates). Thus, installation-specific templates override both 
          default and extension templates.
        </para>
      </listitem>

      <listitem>
        <para>
          If you are looking to customize Bugzilla, you can also take advantage 
          of template hooks. To do so, create a directory in
          <filename>BUGZILLA_ROOT/template/en/custom/hook/</filename>
          that corresponds to the hook you wish to use, then place your 
          customization templates into those directories. For example, 
          if you wanted to use the hook "end" in 
          <filename>global/useful-links.html.tmpl</filename>, you would 
          create the directory <filename>BUGZILLA_ROOT/template/en/custom/hook/
          global/useful-links.html.tmpl/end/</filename> and add your customization 
          template to this directory. 
        </para>

        <para>
          Obviously this method of customizing Bugzilla only lets you add code
          to the standard source files and templates; you cannot change the 
          existing code. Nevertheless, for those customizations that only add 
          code, this method can reduce conflicts when merging changes, 
          making upgrading your customized Bugzilla installation easier.
        </para>
      </listitem>
    </itemizedlist>    
  </section>

  <section id="cust-change-permissions">
    <title>Customizing Who Can Change What</title>
    
    <warning>
      <para>
        This feature should be considered experimental; the Bugzilla code you
        will be changing is not stable, and could change or move between 
        versions. Be aware that if you make modifications as outlined here, 
        you may have
        to re-make them or port them if Bugzilla changes internally between
        versions, and you upgrade.
      </para>
    </warning>
       
    <para>
      Companies often have rules about which employees, or classes of employees,
      are allowed to change certain things in the bug system. For example, 
      only the bug's designated QA Contact may be allowed to VERIFY the bug.
      Bugzilla has been
      designed to make it easy for you to write your own custom rules to define
      who is allowed to make what sorts of value transition.
    </para>
    
    <para>
      For maximum flexibility, customizing this means editing Bugzilla's Perl 
      code. This gives the administrator complete control over exactly who is
      allowed to do what. The relevant function is called 
      <filename>CheckCanChangeField()</filename>,
      and is found in <filename>process_bug.cgi</filename> in your 
      Bugzilla directory. If you open that file and search for 
      <quote>sub CheckCanChangeField</quote>, you'll find it.
    </para>
    
    <para>
      This function has been carefully commented to allow you to see exactly
      how it works, and give you an idea of how to make changes to it.
      Certain marked sections should not be changed - these are
      the <quote>plumbing</quote> which makes the rest of the function work.
      In between those sections, you'll find snippets of code like:
      <programlisting>    # Allow the assignee to change anything.
    if ($ownerid eq $whoid) {
        return 1;
    }</programlisting>
      It's fairly obvious what this piece of code does.
    </para>      
      
    <para>
      So, how does one go about changing this function? Well, simple changes
      can be made just by removing pieces - for example, if you wanted to 
      prevent any user adding a comment to a bug, just remove the lines marked
      <quote>Allow anyone to change comments.</quote> If you don't want the
      Reporter to have any special rights on bugs they have filed, just
      remove the entire section that deals with the Reporter.
    </para>
    
    <para>
      More complex customizations are not much harder. Basically, you add
      a check in the right place in the function, i.e. after all the variables
      you are using have been set up. So, don't look at $ownerid before 
      $ownerid has been obtained from the database. You can either add a
      positive check, which returns 1 (allow) if certain conditions are true,
      or a negative check, which returns 0 (deny.) E.g.:
      <programlisting>    if ($field eq "qacontact") {
        if (Bugzilla->user->groups("quality_assurance")) {
            return 1;
        } 
        else {
            return 0;
        }
    }</programlisting>
      This says that only users in the group "quality_assurance" can change
      the QA Contact field of a bug.
    </para>

    <para>
      Getting more weird:
      <programlisting><![CDATA[    if (($field eq "priority") &&
        (Bugzilla->user->email =~ /.*\@example\.com$/))
    {
        if ($oldvalue eq "P1") {
            return 1;
        } 
        else {
            return 0;
        }
    }]]></programlisting>
      This says that if the user is trying to change the priority field,
      and their email address is @example.com, they can only do so if the
      old value of the field was "P1". Not very useful, but illustrative.
    </para>

    <warning>
      <para>
        If you are modifying <filename>process_bug.cgi</filename> in any
        way, do not change the code that is bounded by DO_NOT_CHANGE blocks.
        Doing so could compromise security, or cause your installation to
        stop working entirely.
      </para>
    </warning>
    
    <para>
      For a list of possible field names, look in 
      <filename>data/versioncache</filename> for the list called 
      <filename>@::log_columns</filename>. If you need help writing custom
      rules for your organization, ask in the newsgroup.
    </para>    
  </section>   
  
  <section id="dbmodify">
    <title>Modifying Your Running System</title>

      <para>
        Bugzilla optimizes database lookups by storing all relatively
        static information in the <filename>versioncache</filename>
        file, located in the <filename class="directory">data/</filename>
        subdirectory under your installation directory.
      </para>

      <para>
        If you make a change to the structural data in your database (the
        versions table for example), or to the <quote>constants</quote>
        encoded in <filename>defparams.pl</filename>, you will need to remove 
        the cached content from the data directory (by doing a 
        <command>rm data/versioncache</command>), or your changes won't show up.
      </para>

      <para>
        <filename>versioncache</filename> gets regenerated automatically
        whenever it's more than an hour old, so Bugzilla will eventually
        notice your changes by itself, but generally you want it to notice
        right away, so that you can test things.
      </para>
    </section>

  <section id="dbdoc">
    <title>MySQL Bugzilla Database Introduction</title>

    <para>This information comes straight from my life. I was forced to learn
    how Bugzilla organizes database because of nitpicky requests from users
    for tiny changes in wording, rather than having people re-educate
    themselves or figure out how to work our procedures around the tool. It
    sucks, but it can and will happen to you, so learn how the schema works
    and deal with it when it comes.</para>

    <para>So, here you are with your brand-new installation of Bugzilla.
    You've got MySQL set up, Apache working right, Perl DBI and DBD talking
    to the database flawlessly. Maybe you've even entered a few test bugs to
    make sure email's working; people seem to be notified of new bugs and
    changes, and you can enter and edit bugs to your heart's content. Perhaps
    you've gone through the trouble of setting up a gateway for people to
    submit bugs to your database via email, have had a few people test it,
    and received rave reviews from your beta testers.</para>

    <para>What's the next thing you do? Outline a training strategy for your
    development team, of course, and bring them up to speed on the new tool
    you've labored over for hours.</para>

    <para>Your first training session starts off very well! You have a
    captive audience which seems enraptured by the efficiency embodied in
    this thing called "Bugzilla". You are caught up describing the nifty
    features, how people can save favorite queries in the database, set them
    up as headers and footers on their pages, customize their layouts,
    generate reports, track status with greater efficiency than ever before,
    leap tall buildings with a single bound and rescue Jane from the clutches
    of Certain Death!</para>

    <para>But Certain Death speaks up -- a tiny voice, from the dark corners
    of the conference room. "I have a concern," the voice hisses from the
    darkness, "about the use of the word 'verified'."</para>

    <para>The room, previously filled with happy chatter, lapses into
    reverential silence as Certain Death (better known as the Vice President
    of Software Engineering) continues. "You see, for two years we've used
    the word 'verified' to indicate that a developer or quality assurance
    engineer has confirmed that, in fact, a bug is valid. I don't want to
    lose two years of training to a new software product. You need to change
    the bug status of 'verified' to 'approved' as soon as possible. To avoid
    confusion, of course."</para>

    <para>Oh no! Terror strikes your heart, as you find yourself mumbling
    "yes, yes, I don't think that would be a problem," You review the changes
    with Certain Death, and continue to jabber on, "no, it's not too big a
    change. I mean, we have the source code, right? You know, 'Use the
    Source, Luke' and all that... no problem," All the while you quiver
    inside like a beached jellyfish bubbling, burbling, and boiling on a hot
    Jamaican sand dune...</para>

    <para>Thus begins your adventure into the heart of Bugzilla. You've been
    forced to learn about non-portable enum() fields, varchar columns, and
    tinyint definitions. The Adventure Awaits You!</para>

    <section>
      <title>Bugzilla Database Basics</title>

      <para>If you were like me, at this point you're totally clueless about
      the internals of MySQL, and if it weren't for this executive order from
      the Vice President you couldn't care less about the difference between
      a 
      <quote>bigint</quote>

      and a 
      <quote>tinyint</quote>

      entry in MySQL. I recommend you refer to the
      <ulink url="http://www.mysql.com/documentation/">MySQL documentation</ulink>
      . Below are the basics you need to know about the Bugzilla database.
      Check the chart above for more details.</para>

      <para>
        <orderedlist>
          <listitem>
            <para>To connect to your database:</para>

            <para>
              <prompt>bash#</prompt>

              <command>mysql</command>

              <parameter>-u root</parameter>
            </para>

            <para>If this works without asking you for a password, 
            <emphasis>shame on you</emphasis>

            ! You should have locked your security down like the installation
            instructions told you to. You can find details on locking down
            your database in the Bugzilla FAQ in this directory (under
            "Security"), or more robust security generalities in the 
            <ulink url="http://www.mysql.com/php/manual.php3?section=Privilege_system">MySQL
            searchable documentation</ulink>.
            </para>
          </listitem>

          <listitem>
            <para>You should now be at a prompt that looks like this:</para>

            <para>
              <prompt>mysql&gt;</prompt>
            </para>

            <para>At the prompt, if 
            <quote>bugs</quote>

            is the name you chose in the
            <filename>localconfig</filename>

            file for your Bugzilla database, type:</para>

            <para>
              <prompt>mysql</prompt>

              <command>use bugs;</command>
            </para>

          </listitem>
        </orderedlist>
      </para>

      <section>
        <title>Bugzilla Database Tables</title>

        <para>Imagine your MySQL database as a series of spreadsheets, and
        you won't be too far off. If you use this command:</para>

        <para>
          <prompt>mysql&gt;</prompt>
          <command>show tables from bugs;</command>
        </para>

        <para>you'll be able to see the names of all the 
        <quote>spreadsheets</quote>
        (tables) in your database.</para>

 	<para>From the command issued above, ou should have some
	  output that looks like this:
<programlisting>
+-------------------+
| Tables in bugs    |
+-------------------+
| attachments       |
| bugs              |
| bugs_activity     |
| cc                |
| components        |
| dependencies      |
| fielddefs         |
| groups            |
| keyworddefs       |
| keywords          |
| logincookies      |
| longdescs         |
| milestones        |
| namedqueries      |
| products          |
| profiles          |
| profiles_activity |
| tokens            |
| versions          |
| votes             |
| watch             |
+-------------------+
</programlisting>
</para>

<literallayout>
  Here's an overview of what each table does. Most columns in each table have
descriptive names that make it fairly trivial to figure out their jobs.

attachments: This table stores all attachments to bugs. It tends to be your
largest table, yet also generally has the fewest entries because file
attachments are so (relatively) large.

bugs:  This is the core of your system. The bugs table stores most of the
current information about a bug, with the exception of the info stored in the
other tables.

bugs_activity:  This stores information regarding what changes are made to bugs
when -- a history file.

cc:  This tiny table simply stores all the CC information for any bug which has
any entries in the CC field of the bug. Note that, like most other tables in
Bugzilla, it does not refer to users by their user names, but by their unique
userid, stored as a primary key in the profiles table.

components: This stores the programs and components (or products and
components, in newer Bugzilla parlance) for Bugzilla. Curiously, the "program"
(product) field is the full name of the product, rather than some other unique
identifier, like bug_id and user_id are elsewhere in the database.

dependencies: Stores data about those cool dependency trees.

fielddefs:  A nifty table that defines other tables. For instance, when you
submit a form that changes the value of "AssignedTo" this table allows
translation to the actual field name "assigned_to" for entry into MySQL.

groups:  defines bitmasks for groups. A bitmask is a number that can uniquely
identify group memberships. For instance, say the group that is allowed to
tweak parameters is assigned a value of "1", the group that is allowed to edit
users is assigned a "2", and the group that is allowed to create new groups is
assigned the bitmask of "4". By uniquely combining the group bitmasks (much
like the chmod command in UNIX,) you can identify a user is allowed to tweak
parameters and create groups, but not edit users, by giving him a bitmask of
"5", or a user allowed to edit users and create groups, but not tweak
parameters, by giving him a bitmask of "6" Simple, huh?
  If this makes no sense to you, try this at the mysql prompt:
mysql> select * from groups;
  You'll see the list, it makes much more sense that way.

keyworddefs:  Definitions of keywords to be used

keywords: Unlike what you'd think, this table holds which keywords are
associated with which bug id's.

logincookies: This stores every login cookie ever assigned to you for every
machine you've ever logged into Bugzilla from. Curiously, it never does any
housecleaning -- I see cookies in this file I've not used for months. However,
since Bugzilla never expires your cookie (for convenience' sake), it makes
sense.

longdescs:  The meat of bugzilla -- here is where all user comments are stored!
You've only got 2^24 bytes per comment (it's a mediumtext field), so speak
sparingly -- that's only the amount of space the Old Testament from the Bible
would take (uncompressed, 16 megabytes). Each comment is keyed to the
bug_id to which it's attached, so the order is necessarily chronological, for
comments are played back in the order in which they are received.

milestones:  Interesting that milestones are associated with a specific product
in this table, but Bugzilla does not yet support differing milestones by
product through the standard configuration interfaces.

namedqueries:  This is where everybody stores their "custom queries". Very
cool feature; it beats the tar out of having to bookmark each cool query you
construct.

products:  What products you have, whether new bug entries are allowed for the
product, what milestone you're working toward on that product, votes, etc. It
will be nice when the components table supports these same features, so you
could close a particular component for bug entry without having to close an
entire product...

profiles:  Ahh, so you were wondering where your precious user information was
stored?  Here it is!  With the passwords in plain text for all to see! (but
sshh... don't tell your users!)

profiles_activity:  Need to know who did what when to who's profile?  This'll
tell you, it's a pretty complete history.

versions:  Version information for every product

votes:  Who voted for what when

watch:  Who (according to userid) is watching who's bugs (according to their
userid).


===
THE DETAILS
===

  Ahh, so you're wondering just what to do with the information above?  At the
mysql prompt, you can view any information about the columns in a table with
this command (where "table" is the name of the table you wish to view):

mysql> show columns from table;

  You can also view all the data in a table with this command:

mysql> select * from table;

  -- note: this is a very bad idea to do on, for instance, the "bugs" table if
you have 50,000 bugs. You'll be sitting there a while until you ctrl-c or
50,000 bugs play across your screen.

  You can limit the display from above a little with the command, where
"column" is the name of the column for which you wish to restrict information:

mysql> select * from table where (column = "some info");

  -- or the reverse of this

mysql> select * from table where (column != "some info");

  Let's take our example from the introduction, and assume you need to change
the word "verified" to "approved" in the resolution field. We know from the
above information that the resolution is likely to be stored in the "bugs"
table. Note we'll need to change a little perl code as well as this database
change, but I won't plunge into that in this document. Let's verify the
information is stored in the "bugs" table:

mysql> show columns from bugs

  (exceedingly long output truncated here)
| bug_status| enum('UNCONFIRMED','NEW','ASSIGNED','REOPENED','RESOLVED','VERIFIED','CLOSED')||MUL | UNCONFIRMED||

  Sorry about that long line. We see from this that the "bug status" column is
an "enum field", which is a MySQL peculiarity where a string type field can
only have certain types of entries. While I think this is very cool, it's not
standard SQL. Anyway, we need to add the possible enum field entry
'APPROVED' by altering the "bugs" table.

mysql> ALTER table bugs CHANGE bug_status bug_status
    -> enum("UNCONFIRMED", "NEW", "ASSIGNED", "REOPENED", "RESOLVED",
    -> "VERIFIED", "APPROVED", "CLOSED") not null;

    (note we can take three lines or more -- whatever you put in before the
semicolon is evaluated as a single expression)

Now if you do this:

mysql> show columns from bugs;

  you'll see that the bug_status field has an extra "APPROVED" enum that's
available!  Cool thing, too, is that this is reflected on your query page as
well -- you can query by the new status. But how's it fit into the existing
scheme of things?
  Looks like you need to go back and look for instances of the word "verified"
in the perl code for Bugzilla -- wherever you find "verified", change it to
"approved" and you're in business (make sure that's a case-insensitive search).
Although you can query by the enum field, you can't give something a status
of "APPROVED" until you make the perl changes. Note that this change I
mentioned can also be done by editing checksetup.pl, which automates a lot of
this. But you need to know this stuff anyway, right?
	</literallayout>
      </section>
    </section>
  </section>

  <!-- Integrating Bugzilla with Third-Party Tools -->
  &integration;

</chapter>

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