[Findit] Check existence of given targets before running compile in recipe findit/chromium/compile.

scripts/slave/recipe_modules/findit/api.py

Index: scripts/slave/recipe_modules/findit/api.py
diff --git a/scripts/slave/recipe_modules/findit/api.py b/scripts/slave/recipe_modules/findit/api.py
index 24db0173609f40c186763dbf5480a66b7dc45d4d..90cefaf2814f17a74ded3ae14429f306204b0621 100644
--- a/scripts/slave/recipe_modules/findit/api.py
+++ b/scripts/slave/recipe_modules/findit/api.py
@@ -78,3 +78,38 @@ class FinditApi(recipe_api.RecipeApi):
 
     step_result.presentation.logs['revisions'] = revisions
     return revisions
+
+  def existing_targets(self, targets, mb_mastername, mb_buildername):
+    """Returns a sublist of the given targets that exist in the build graph.
+
+    We test whether a target exists or not by ninja.
+
+    A "target" here is actually a node in ninja's build graph. For example:
+      1. An executable target like browser_tests
+      2. An object file like obj/path/to/Source.o
+      3. An action like build/linux:gio_loader
+      4. An generated header file like gen/library_loaders/libgio.h
+      5. and so on
+
+    Args:
+     targets (list): A list of targets to be tested for existence.
+     mb_mastername (str): The mastername to run MB with.
+     mb_buildername (str): The buildername to run MB with.
+    """
+    # Run mb to generate or update ninja build files.
+    if self.m.chromium.c.project_generator.tool == 'mb':
+      self.m.chromium.run_mb(mb_mastername, mb_buildername,
+                             name='generate_build_files')

[Nico, 2016/03/08 19:41:36]

I suppose this assumes we don't need this with gyp? Will this do the right thing
(which I guess is "don't run this function there"?) on bots that still use gyp

[stgao, 2016/03/09 20:09:11]

I think so. If the project generator tool is gyp, src/build/gyp_chromium is run
by runhooks as part of the code checkout,
https://code.google.com/p/chromium/codesearch#chromium/build/scripts/slave/re...
.

I will double check with Dirk on this.

+
+    # Run ninja to check existences of targets.
+    args = []
+    args.extend(['--target-build-dir', self.m.chromium.output_dir])

[Nico, 2016/03/08 19:41:36]

nit: replace previous two lines with

  args = ['--target-build-dir', self.m.chromium.output_dir]

[stgao, 2016/03/09 20:09:11]

Done.

+    for target in targets:
+      args.extend(['--target', target])
+    args.extend(['--json-output', self.m.json.output()])
+    step = self.m.python(
+        'check_targets',
+        self.m.path['build'].join(
+            'scripts', 'slave', 'check_target_existence.py'),
+        args=args)
+    return step.json.output['found']

[Nico, 2016/03/08 19:41:36]

If you don't need the not_found output, why write it?

[stgao, 2016/03/09 20:09:11]

Removed.
Original idea is to keep them for completeness as the script is added to a
shared location.