Edgewall Software

0.11 | 1.0

TracDev/ApiChanges/0.12

Summary

  1. Prerequisites
    1. Modified Dependencies
    2. New Dependencies
      1. Babel (optional)
  2. Modifications made to the 0.12 API
    1. Modified Interfaces
      1. IWikiMacroProvider (0.12)​ (0.11)​
      2. IWikiPageManipulator (0.12)​ (0.11)​
    2. Other Changes
      1. Environment.get_db_cnx is deprecated
      2. prevnext_nav support for i18n (0.12)​ (0.11)​
      3. Href with an empty base (0.12)​ (0.11)​
      4. tracd and HTTP/1.1
      5. Environment.get_repository() (0.12)​ (0.11)​
      6. Authz permission checking
      7. Repository constructor (0.12)​ (0.11)​
      8. Repository revision transformation (0.12)​
      9. Node constructor (0.12)​ (0.11)​
      10. Changeset constructor (0.12)​ (0.11)​
      11. CachedRepository constructor (0.12)​ (0.11)​
      12. Text template syntax
      13. Timestamp storage in database
  3. New in the 0.12 API
    1. New Classes
      1. trac.cache.CacheManager (0.12)​
      2. trac.util.text.empty (0.12)​
    2. New Interfaces
      1. trac.admin.api.IAdminCommandProvider (0.12)​
      2. trac.env.ISystemInfoProvider (0.12)​
      3. trac.ticket.api.IMilestoneChangeListener (0.12)​
      4. trac.versioncontrol.api.IRepositoryChangeListener (0.12)​
      5. trac.versioncontrol.api.IRepositoryProvider (0.12)​
    3. Other news
      1. trac.db.util.with_transaction() (0.12)​

Prerequisites

Python 2.3 support has been dropped. Python versions 2.4, 2.5, 2.6 and 2.7 are supported.

Modified Dependencies

The bundled version of jQuery is now 1.4.2 instead of 1.2.6 in Trac 0.11. Among other things, this means that previously deprecated selector syntax is now no longer supported. See jQuery 1.3 API changes, jQuery 1.4 API changes and jQuery 1.4.1 API changes for details.

New Dependencies

Babel (optional)

The internationalization support (i18) for Trac is depending on Babel.

It's perfectly fine to go on using Trac without it, but then of course the interface will remain in English.

Modifications made to the 0.12 API

Modified Interfaces

IWikiMacroProvider (0.12) (0.11)

Added an optional argument args to IWikiMacroProvider.expand_macro() to contain the shebang-line arguments when using wiki processor syntax. For example, with the following content:

{{{
#!MyMacro test=123 other="This is a text"
This is the content.
}}}

The macro MyMacro will have its expand_macro() called with args={'test': '123', 'other': 'This is a text'}.

See also #8204.

IWikiPageManipulator (0.12) (0.11)

This interface has not actually been changed, but the implementation has been fixed so that it actually does what it promises, that is, validate a wiki page after it's been populated from user input. Previously, page.text would contain the old text, and the new text would typically be retrieved with req.args.get('text') as a workaround.

The page now has the new text in page.text, and the old text in page.old_text.

See also #7731.

Other Changes

Environment.get_db_cnx is deprecated

Due to the new support for automated transaction management, Connection instances should no longer be acquired using the familiar get_db_cnx method, as it doesn't tell whether the connection will be used as part of a write transaction or purely for queries. Instead, one should use:

  • env.get_read_db for obtaining a Connection suitable for read queries (i.e. SELECT)
  • the env.with_transaction decorator, for using a db parameter in a transaction function which should be committed when the last such automatic transaction in the control flow completes successfully (see details further down)

Using env.get_db_cnx still works, but any explicit transaction management will risk to prematurely end a higher level transaction set up via with_transaction at a previous level in the control flow.

prevnext_nav support for i18n (0.12) (0.11)

The prevnext_nav function used for adding contextual navigation links was not i18n friendly. In order to make the need for adaptation obvious, the arity of the function has changed and the label for the previous and next links have to be spelled out in full.

Href with an empty base (0.12) (0.11)

The Href class has been changed to ensure that it always generates valid URLs, even with an empty base. In 0.11, the following uses all return an empty string:

# 0.11
>>> href = Href('')             # Also applies to Href('/')
>>> href()
''
>>> href('/')
''

In 0.12, the same expressions return a valid relative URL:

# 0.12
>>> href = Href('')
>>> href()
'/'
>>> href('/')
'/'

This change will break plugins that use the following idiom to concatenate the base URL with a path starting with a slash:

# 0.12
>>> href = Href('')
>>> path = '/path/to/page'
>>> href() + path               # Broken
'//path/to/page'

For this specific use case, a new syntax has been added to avoid doubled slashes:

# 0.12 and 0.11.6
>>> href = Href('')
>>> path = '/path/to/page'
>>> href + path                 # New syntax
'/path/to/page'

The new syntax has been backported to 0.11-stable in 0.11.6 to facilitate compatibility of plugins with both 0.11.6 and 0.12. If compatibility with older releases of the 0.11.x branch is required, the following code can be used:

# 0.12 and 0.11.x
>>> href = Href('')
>>> path = '/path/to/page'
>>> href().rstrip('/') + path   # Compatibility
'/path/to/page'

See also #8159.

tracd and HTTP/1.1

Since 0.11.5, tracd could be used with the --http11 flag, which would select the use of the HTTP/1.1 protocol and most notably activate Keep-Alive connections. This is now the default behavior in 0.12.

This has some important consequences for plugins which send content directly to the client. They should take care of setting the Content-Length header properly, otherwise the browser will simply "hang".

This means that any:

    req.write(content)

must be preceded by a:

    req.send_header('Content-Length', len(content))

Don't forget to do that for any data directly sent back to the client, including responses for XHRs (e.g. r8300). This requires some discipline in the coding, but the benefit is a huge performance boost for tracd, so it's well worth the price.

In order to make errors more immediately visible, the Request.write method is more strict in 0.12: it only accepts str data parameter, and will also raise an exception if the Content-Length header was not set prior to the call.

See #8020 and #8675 for details.

Environment.get_repository() (0.12) (0.11)

The standard way of retrieving a repository object is now through the methods of RepositoryManager. The method Environment.get_repository() has been retained for backward compatibility, and a new argument reponame has been added to allow retrieving other repositories than the default repository. The authname argument has been kept for backward compatibility, but is not used anymore (see authz permission checking below).

Authz permission checking

Permission checking using an authz-type file has been moved from an Authorizer instance used by SubversionRepository to a fine-grained permission policy AuthzSourcePolicy defined in svn_authz.py. This allows using authz files not only for Subversion repositories, but also for other repository types.

Consequently, the Authorizer, PermissionDenied and RealSubversionAuthorizer classes as well as the SubversionAuthorizer function have been removed.

See #7116 for details.

Repository constructor (0.12) (0.11)

Due to the authz changes above, the authz argument has been removed from the Repository constructor.

Conversely, a new argument params has been added to the Repository constructor. params is a dictionary containing various parameters for the repository, and is stored as a .params attribute in Repository. The value for the key "name" is the repository name (available as .reponame) as displayed in the source browser. The value for the key "id" (available as .id) is the surrogate key identifying the repository in the database.

Both changes need to be taken into account by derived classes (typically in plugins implementing version control backends), which must propagate the arguments up to Repository.__init__()

See #7116 for details on the authz argument, and #8731 for the params argument.

Repository revision transformation (0.12)

In addition to Repository.normalize_rev(rev), which returns a (unique) normalized representation of the given revision (usually a full revision number or hash), and Repository.short_rev(rev), which returns a short representation of the a revision to be used e.g. for source annotation, a new Repository.display_rev(rev) method can be implemented by version control backends to return a representation of a revision suitable for display to the user. By default, display_rev() calls normalize_rev().

See #9230 for details.

Node constructor (0.12) (0.11)

The Repository instance to which a node belongs is now passed as an additional repos argument to the Node constructor, and stored in the .repos attribute. This argument must be forwarded by Node subclasses (typically in plugins implementing version control backends).

See #7116 for details.

Changeset constructor (0.12) (0.11)

The Repository instance to which a changeset belongs is now passed as an additional repos argument to the Changeset constructor, and stored in the .repos attribute. This argument must be forwarded by Changeset subclasses (typically in plugins implementing version control backends).

See #7116 for details.

CachedRepository constructor (0.12) (0.11)

In 0.11, the first argument to the CachedRepository constructor was a callable that would return a DB instance when called. In 0.12, the first argument has been changed to an Environment instance. Subclasses of CachedRepository must therefore be changed accordingly, and components implementing IRepositoryConnector and returning a CachedRepository or a subclass must pass self.env instead of a getdb callable.

Moreover, the authz argument has been removed as well, as described above.

Text template syntax

Text template processing has been changed from the legacy text template syntax to the new text template syntax. The main difference is that directives are now enclosed in {% %} and can be placed anywhere in the text, whereas they were previously placed on their own line with a leading #.

All text templates used by plugins must therefore be converted to the new syntax. The same applies to overridden templates placed in the templates folder of environments.

See #8513 for details.

Timestamp storage in database

Timestamps associated with resources and stored in the database have been changed from second to microsecond resolution. This should not affect plugins that use the model classes to access resources. However, plugins accessing the database tables directly need to be adapted.

Conversion between datetime objects and microsecond timestamps can be performed with the new functions from_utimestamp() and to_utimestamp() in trac/util/datefmt.py.

See #6466 for details.

New in the 0.12 API

New Classes

trac.cache.CacheManager (0.12)

There's a new cache subsystem in trac.cache allowing Component instances to cache any data in a safe way. Whenever the cache entry is invalidated, the cached value will be automatically refreshed at the next retrieval, even if the invalidation occurs in a different process. This makes the config.touch() trick obsolete.

New decorator: trac.cache.cached (0.12)

See TracDev/CacheManager for details.

trac.util.text.empty (0.12)

Special marker object used to represent a NULL value from the database as an empty string, yet be able to distinguish it from '' when really necessary.

New Interfaces

trac.admin.api.IAdminCommandProvider (0.12)

The IAdminCommandProvider interface allows components to provide additional trac-admin commands. It supports short and long help texts, as well as command and argument auto-completion.

See #7770 for details.

trac.env.ISystemInfoProvider (0.12)

The ISystemInfoProvider interface allows components to provide version information about external packages they use. This information is displayed on the "About Trac" page, as well as in internal error reports. This interface replaces the direct mutation of the env.systeminfo list that was used previously (the list is still present for backward compatibility). The advantage of using an interface for this is that it ensures that the components are loaded when the system information is requested.

See #8908 for details.

trac.ticket.api.IMilestoneChangeListener (0.12)

Components implementing the IMilestoneChangeListener interface are notified upon creation, modification and deletion of milestones. The milestone model object is passed to each handler. Moreover, on modification an additional dictionary is passed, containing the attributes that were modified and their previous values.

See #6543 for details.

trac.versioncontrol.api.IRepositoryChangeListener (0.12)

Components implementing the IRepositoryChangeListener interface are notified when new changesets are added to a repository, and when metadata for changesets is modified. Both events are generated by trac-admin $ENV changeset commands, and therefore require that hooks in the repositories call these commands on commit and revision property changes, as described in TracRepositoryAdmin.

See #7723 for details.

trac.versioncontrol.api.IRepositoryProvider (0.12)

Components implementing IRepositoryProvider provide information about repositories managed by a Trac instance. There are currently two components implementing this interface: the first one extracts repository information from the [repositories] section of trac.ini, the second from the database.

Plugins can implement additional providers, for example to automatically include all repositories located below a given directory (similar to the SVNParentPath directive of mod_dav_svn).

Other news

trac.db.util.with_transaction() (0.12)

The @with_transaction(env) decorator replaces the current practice of getting a database connection with env.get_db_cnx() and issuing an explicit commit or rollback. Applied to a local function, it calls that function with a database connection as an argument, and either issues a commit if the function terminates normally, or a rollback if the function raises an exception. In the latter case, the exception is re-raised.

This makes transactions much more robust, as we can guarantee that any mutating operations on the database are either committed or rolled back. This should avoid issues like #8443, where transactions were kept open in IDLE state.

This mechanism also handles transaction nesting automatically, by only committing or rolling back in the outermost transaction block. This avoids having to pass a db argument around, like was typically done in model object methods like WikiPage.save(). The db argument is still supported for backward compatibility in methods that were present in 0.11, but is deprecated and should not be used in new code.

To avoid having to import with_transaction from trac.db.util in every module using transactions, it can also be called conveniently on the environment as @env.with_transaction().

Implementing this mechanism as a function decorator is an intermediate solution until the with statement and context managers become available (once we drop support for Python 2.4).

See #8751 for details and related notes about get_db_cnx deprecation above.

Last modified 19 months ago Last modified on Sep 16, 2012 11:27:18 AM