recipes: cache destination branch of a Gerrit change.

It doesn't change after change is created.

R=jchinlee@chromium.org

Recipe-Nontrivial-Roll: build
Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Change-Id: I4c4758085f6cfa7c2ef5267c6c71c9b324263f95
Reviewed-on: https://chromium-review.googlesource.com/1029227
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>

recipes/README.recipes.md

@@ -309,18 +309,18 @@ revision map. This doesn't overwrite the revision if it was already set.
 
 Module for interact with gerrit endpoints
 
-— **def [\_\_call\_\_](/recipes/recipe_modules/gerrit/api.py#10)(self, name, cmd, infra_step=True, \*\*kwargs):**
+— **def [\_\_call\_\_](/recipes/recipe_modules/gerrit/api.py#14)(self, name, cmd, infra_step=True, \*\*kwargs):**
 
 Wrapper for easy calling of gerrit_utils steps.
 
-— **def [create\_gerrit\_branch](/recipes/recipe_modules/gerrit/api.py#27)(self, host, project, branch, commit, \*\*kwargs):**
+— **def [create\_gerrit\_branch](/recipes/recipe_modules/gerrit/api.py#31)(self, host, project, branch, commit, \*\*kwargs):**
 
 Create a new branch from given project and commit
 
 Returns:
   the ref of the branch created
 
-— **def [get\_change\_description](/recipes/recipe_modules/gerrit/api.py#93)(self, host, change, patchset):**
+— **def [get\_change\_description](/recipes/recipe_modules/gerrit/api.py#106)(self, host, change, patchset):**
 
 Get the description for a given CL and patchset.
 
@@ -332,10 +332,12 @@ Args:
 Returns:
   The description corresponding to given CL and patchset.
 
-— **def [get\_change\_destination\_branch](/recipes/recipe_modules/gerrit/api.py#68)(self, host, change, \*\*kwargs):**
+— **def [get\_change\_destination\_branch](/recipes/recipe_modules/gerrit/api.py#72)(self, host, change, name=None, step_test_data=None):**
 
 Get the upstream branch for a given CL.
 
+Result is cached.
+
 Args:
   host: Gerrit host to query.
   change: The change number.
@@ -343,7 +345,7 @@ Args:
 Returns:
   the name of the branch
 
-— **def [get\_changes](/recipes/recipe_modules/gerrit/api.py#122)(self, host, query_params, start=None, limit=None, o_params=None, step_test_data=None, \*\*kwargs):**
+— **def [get\_changes](/recipes/recipe_modules/gerrit/api.py#135)(self, host, query_params, start=None, limit=None, o_params=None, step_test_data=None, \*\*kwargs):**
 
 Query changes for the given host.
 
@@ -361,7 +363,7 @@ Returns:
   A list of change dicts as documented here:
       https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
 
-— **def [get\_gerrit\_branch](/recipes/recipe_modules/gerrit/api.py#49)(self, host, project, branch, \*\*kwargs):**
+— **def [get\_gerrit\_branch](/recipes/recipe_modules/gerrit/api.py#53)(self, host, project, branch, \*\*kwargs):**
 
 Get a branch from given project and commit
 

recipes/recipe_modules/gerrit/api.py

@@ -7,6 +7,10 @@ from recipe_engine import recipe_api
 class GerritApi(recipe_api.RecipeApi):
   """Module for interact with gerrit endpoints"""
 
+  def __init__(self, *args, **kwargs):
+    super(GerritApi, self).__init__(*args, **kwargs)
+    self._changes_target_branch_cache = {}
+
   def __call__(self, name, cmd, infra_step=True, **kwargs):
     """Wrapper for easy calling of gerrit_utils steps."""
     assert isinstance(cmd, (list, tuple))
@@ -65,10 +69,13 @@ class GerritApi(recipe_api.RecipeApi):
     revision = step_result.json.output.get('revision')
     return revision
 
-  def get_change_destination_branch(self, host, change, **kwargs):
+  def get_change_destination_branch(
+      self, host, change, name=None, step_test_data=None):
     """
     Get the upstream branch for a given CL.
 
+    Result is cached.
+
     Args:
       host: Gerrit host to query.
       change: The change number.
@@ -76,19 +83,25 @@ class GerritApi(recipe_api.RecipeApi):
     Returns:
       the name of the branch
     """
-    assert int(change)
+    assert int(change), change
-    kwargs.setdefault('name', 'get_change_destination_branch')
+    change = int(change)
+    branch = self._changes_target_branch_cache.get((host, change))
+    if branch is not None:
+      return branch
     changes = self.get_changes(
         host,
         [('change', change)],
         limit=1,
-        **kwargs
+        name=name or 'get_change_destination_branch',
+        step_test_data=step_test_data,
     )
     if not changes or 'branch' not in changes[0]:
       self.m.step.active_result.presentation.status = self.m.step.EXCEPTION
       raise self.m.step.InfraFailure(
           'Error quering for branch of CL %s' % change)
-    return changes[0]['branch']
+    branch = changes[0]['branch']
+    self._changes_target_branch_cache[(host, change)] = branch
+    return branch
 
   def get_change_description(self, host, change, patchset):
     """

recipes/recipe_modules/gerrit/examples/full.expected/basic.json

@@ -213,7 +213,7 @@
       "--limit",
       "1",
       "-p",
-      "change=123"
+      "change=122"
     ],
     "env": {
       "PATH": "<PATH>:RECIPE_PACKAGE_REPO[depot_tools]"
@@ -239,7 +239,7 @@
       "--limit",
       "1",
       "-p",
-      "change=123",
+      "change=122",
       "-o",
       "ALL_REVISIONS",
       "-o",
@@ -276,7 +276,7 @@
   },
   {
     "name": "$result",
-    "reason": "2 out of 2 aggregated steps failed. Failures: Error quering for branch of CL 123, Error querying for CL description: host:'https://chromium-review.googlesource.com' change:123; patchset:3",
+    "reason": "2 out of 2 aggregated steps failed. Failures: Error quering for branch of CL 122, Error querying for CL description: host:'https://chromium-review.googlesource.com' change:122; patchset:3",
     "recipe_result": null,
     "status_code": 1
   }

recipes/recipe_modules/gerrit/examples/full.py

@@ -36,14 +36,17 @@ def RunSteps(api):
   api.gerrit.get_change_description(
       host, change=123, patchset=1)
 
-  api.gerrit.get_change_destination_branch(host, change=123)
+  first = api.gerrit.get_change_destination_branch(host, change=123)
+  # Second call returns cached data.
+  second = api.gerrit.get_change_destination_branch(host, change=123)
+  assert first == second
 
   with api.step.defer_results():
     api.gerrit.get_change_destination_branch(
-        host, change=123, name='missing_cl')
+        host, change=122, name='missing_cl')
 
     api.gerrit.get_change_description(
-        host, change=123, patchset=3)
+        host, change=122, patchset=3)
 
 
 def GenTests(api):