commit 9fa97a4ee7b5126be61eeb215fea02475e5350e3
author Edwin Kempin <ekempin@google.com> Fri Feb 26 16:41:34 2021 +0100
committer Edwin Kempin <ekempin@google.com> Sat Feb 27 21:23:16 2021 +0100
tree 1f05d1fb55d546762f01c4c0a20f1be51503f87f
parent 135b28f87ce7ca4e4e9fd13a2d1a656bb197487e

Refactor config reading as preparation to reduce plugin config loads

Loading a plugin config with inheritance via
pluginConfigFactory#getProjectPluginConfigWithInheritance(projectName,
pluginName) is not free as it needs to overlay the config with the
configs of the parent projects. All configs are cached in the project
cache but doing the overlaying too often can still get expensive. At the
moment we do the overlaying each time a config parameter is read and
since we have a lot of config parameters that get read all over the
code this sums up.

At the moment to read a config parameter we do:
1. get CodeOwnersPluginConfiguration injected
2. call getFoo(Project.NameKey) or getFoo(BranchNameKey) on the
   CodeOwnersPluginConfiguration

Each codeOwnersPluginConfiguration.getFoo(...) call
invokes pluginConfigFactory#getProjectPluginConfigWithInheritance(projectName,
pluginName).

With this change we refactor these calls to:
codeOwnersPluginConfiguration.getProjectConfig(Project.NameKey).getFoo()
and codeOwnersPluginConfiguration.getProjectConfig(Project.NameKey).getFoo(branchName).

codeOwnersPluginConfiguration.getProjectConfig(Project.NameKey) returns
a CodeOwnersPluginConfigSnapshot.

The advantage of the new CodeOwnersPluginConfigSnapshot class is that it
can cache the loaded plugin config and reuse it for subsequent get
calls. With this change we do not benefit from this yet, since all
places that read a config call
codeOwnersPluginConfiguration.getProjectConfig(Project.NameKey) newly
which each time creates a new CodeOwnersPluginConfigSnapshot instance.
However this will change with the follow-up changes. It's not done in
this change yet, so that the refactoring (this change) is separated from
doing improvements (follow-up changes) and hence is hopefully easier to
review.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I3ac34367fdbcdaac299f2c76725e48415683b82b