bug 1052744 - Add mozbuild.makeutil.write_dep_makefile. r=gps

python/mozbuild/mozbuild/makeutil.py

@@ -172,3 +172,13 @@ def read_dep_makefile(fh):
 
     if rule:
         raise Exception('Makefile finishes with a backslash. Expected more input.')
+
+def write_dep_makefile(fh, target, deps):
+    '''
+    Write a Makefile containing only target's dependencies to the file handle
+    specified.
+    '''
+    mk = Makefile()
+    rule = mk.create_rule(targets=[target])
+    rule.add_dependencies(deps)
+    mk.dump(fh, removal_guard=True)

python/mozbuild/mozbuild/test/test_makeutil.py

@@ -6,6 +6,7 @@ from mozbuild.makeutil import (
     Makefile,
     read_dep_makefile,
     Rule,
+    write_dep_makefile,
 )
 from mozunit import main
 import os
@@ -153,5 +154,12 @@ class TestMakefile(unittest.TestCase):
         self.assertEqual(list(result[1].targets()), ['baz', 'qux'])
         self.assertEqual(list(result[1].dependencies()), ['hoge', 'piyo', 'fuga'])
 
+    def test_write_dep_makefile(self):
+        out = StringIO()
+        write_dep_makefile(out, 'target', ['b', 'c', 'a'])
+        self.assertEqual(out.getvalue(),
+                         'target: b c a\n' +
+                         'a b c:\n')
+
 if __name__ == '__main__':
     main()