Patch for bug 298341: Implement code hook mechanism; patch by…

docs/en/xml/customization.xml

@@ -411,11 +411,11 @@
   </section>
 
   <section id="cust-hooks">
-    <title>Template Hooks</title>
+    <title>The Bugzilla Extension Mechanism</title>
         
     <warning>
       <para>
-        Template Hooks require Template Toolkit version 2.12 or
+        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.
@@ -423,62 +423,82 @@
     </warning>
        
     <para>
-      Template hooks are a way for extensions to Bugzilla to insert code
-      into the standard Bugzilla templates without modifying the template files
-      themselves.  The hooks mechanism defines a consistent API for extending
-      the standard templates 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.
+      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 template hook is just a named place in a standard template file
-      where extension template files for that hook get processed.  Each hook
-      has a corresponding directory in the Bugzilla directory tree.  Hooking an
-      extension template to a hook is as simple as putting the extension file
-      into the hook's directory.  When Bugzilla processes the standard template
-      and reaches the hook, it will process all extension templates in the
-      hook's directory. The hooks themselves can be added into any standard
-      template upon request by extension authors.
+      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 a Bugzilla template, first make sure there is
-      a hook at the appropriate place within the template you want to extend. 
-      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 (within that template)
-      name of the hook.
+      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>
-      If you aren't sure which template 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 browse
-      the directory tree in
-      <filename>BUGZILLA_ROOT/template/en/extension/hook/</filename>,
-      which contains a directory for each hook in the following location:
+      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 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>
-      <filename>BUGZILLA_ROOT/template/en/extension/hook/PATH_TO_STANDARD_TEMPLATE/STANDARD_TEMPLATE_NAME/HOOK_NAME/</filename>
+      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 occurences of <methodname>Bugzilla::Hook::process</methodname>.
     </para>
 
     <para>
-      If there is no hook at the appropriate place within the Bugzilla template
-      you want to extend,
+      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 template for which you are requesting a hook;</member>
+      <member>the source or template file for which you are 
+          requesting a hook;</member>
       <member>
-        where in the template you would like the hook to be placed
-        (line number/position for latest version of template in CVS
+        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>
@@ -487,9 +507,8 @@
 
     <para>
       The Bugzilla reviewers will promptly review each hook request,
-      name the hook, add it to the template, check the new version
-      of the template into CVS, and create the corresponding directory in
-      <filename>BUGZILLA_ROOT/template/en/extension/hook/</filename>.
+      name the hook, add it to the template or source file, and check 
+      the new version of the template into CVS.
     </para>
 
     <para>
@@ -505,13 +524,13 @@
 
     <para>
       After making sure the hook you need exists (or getting it added if not),
-      add your extension template to the directory within the Bugzilla
-      directory tree corresponding to the hook. 
+      add your extension to the directory within the Bugzilla
+      extensions tree corresponding to the hook. 
     </para>
     
     <para>
-      That's it!  Now, when the standard template containing the hook
-      is processed, your extension template will be processed at the point 
+      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>
 
@@ -542,14 +561,9 @@
 ...]]></programlisting>
 
     <para>
-      The corresponding directory for this hook is
-      <filename>BUGZILLA_ROOT/template/en/extension/hook/global/useful-links.html.tmpl/edit/</filename>.
-    </para>
-
-    <para>
-      You put a template named
-      <filename>projman-edit-projects.html.tmpl</filename>
-      into that directory with the following content:
+      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>
@@ -558,7 +572,28 @@
       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>
@@ -566,61 +601,47 @@
     <itemizedlist>
       <listitem>
         <para>
-          You may want to prefix your extension template names
-          with the name of your extension, e.g. 
-          <filename>projman-foo.html.tmpl</filename>, 
-          so they do not conflict with the names of templates installed by
-          other extensions.
-        </para>
-      </listitem>
-
-      <listitem>
-        <para>
           If your extension includes entirely new templates in addition to
-          extensions of standard templates, it should install those new
-          templates into an extension-specific subdirectory of the
-          <filename>BUGZILLA_ROOT/template/en/extension/</filename> 
-          directory.  The <filename>extension/</filename> directory, like the 
+          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, is part of the template search path, so putting templates
+          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>extension/</filename> 
-          directory (i.e. templates added by extensions), and finally in 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 extension templates can override standard templates,
-          but installation-specific templates override both.
-        </para>
-
-        <para>
-          Note that overriding standard templates with extension templates
-          gives you great power but also makes upgrading an installation harder.
-          As with custom templates,  we recommend using this functionality
-          sparingly and only when absolutely necessary.
+          templates). Thus, installation-specific templates override both 
+          default and extension templates.
         </para>
       </listitem>
 
       <listitem>
         <para>
-          Installation customizers can also take advantage of hooks when adding
-          code to a Bugzilla template.  To do so, create directories in
+          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>
-          equivalent to the directories in
-          <filename>BUGZILLA_ROOT/template/en/extension/hook/</filename>          
-          for the hooks you want to use, then place your customization templates
-          into those directories.
+          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 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.
+          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>