Bug 818246 - Part 2: Support moz.build -> Makefile variable passthru; r=glandium

--HG--
extra : rebase_source : c9a914e1466e74d079383ef1162a4d1f9959a05c

python/mozbuild/mozbuild/backend/recursivemake.py

@@ -14,6 +14,7 @@ from ..frontend.data import (
     ConfigFileSubstitution,
     DirectoryTraversal,
     SandboxDerived,
+    VariablePassthru,
 )
 from ..util import FileAvoidWrite
 
@@ -178,6 +179,15 @@ class RecursiveMakeBackend(BuildBackend):
             self._update_from_avoid_write(
                 backend_file.environment.create_config_file(obj.output_path))
             self.summary.managed_count += 1
+        elif isinstance(obj, VariablePassthru):
+            # Sorted so output is consistent and we don't bump mtimes.
+            for k, v in sorted(obj.variables.items()):
+                if isinstance(v, list):
+                    for item in v:
+                        backend_file.write('%s += %s\n' % (k, item))
+
+                else:
+                    backend_file.write('%s := %s\n' % (k, v))
 
         self._backend_files[obj.srcdir] = backend_file
 

python/mozbuild/mozbuild/frontend/data.py

@@ -120,3 +120,19 @@ class ConfigFileSubstitution(SandboxDerived):
         self.output_path = None
         self.relpath = None
 
+
+class VariablePassthru(SandboxDerived):
+    """A dict of variables to pass through to backend.mk unaltered.
+
+    The purpose of this object is to facilitate rapid transitioning of
+    variables from Makefile.in to moz.build. In the ideal world, this class
+    does not exist and every variable has a richer class representing it.
+    As long as we rely on this class, we lose the ability to have flexibility
+    in our build backends since we will continue to be tied to our rules.mk.
+    """
+    __slots__ = ('variables')
+
+    def __init__(self, sandbox):
+        SandboxDerived.__init__(self, sandbox)
+        self.variables = {}
+

python/mozbuild/mozbuild/frontend/emitter.py

@@ -7,8 +7,9 @@ from __future__ import unicode_literals
 import os
 
 from .data import (
-    DirectoryTraversal,
     ConfigFileSubstitution,
+    DirectoryTraversal,
+    VariablePassthru,
     ReaderSummary,
 )
 
@@ -69,6 +70,14 @@ class TreeMetadataEmitter(object):
             sub.relpath = path
             yield sub
 
+        # Proxy some variables as-is until we have richer classes to represent
+        # them. We should aim to keep this set small because it violates the
+        # desired abstraction of the build definition away from makefiles.
+        passthru = VariablePassthru(sandbox)
+
+        if passthru.variables:
+            yield passthru
+
     def _emit_directory_traversal_from_sandbox(self, sandbox):
         o = DirectoryTraversal(sandbox)
         o.dirs = sandbox.get('DIRS', [])