Mojo: Make the bindings generator able to dynamically load a generator.

Notes:
- Currently --generators=.../generators/mojom_cpp_generator.py won't
  work; the python module path won't be right for it to just do "import
  mojom" (etc.). Instead, an explicitly-specified generator would have
  to do something like "from generators import mojom".
- @UseJinja's path_to_template argument is now relative to the directory
  containing the *caller's* file (i.e., the generator's file), not the
  directory containing template_expander.py.

Still to do:
- Factory out the generator "library" files to a separate directory,
  away from specific (e.g., C++) generators. (Maybe move all the
  libraries into a pylib/ directory, and add that directory to the
  module path.)
- Make it so that --generators=.../mojom_cpp_generator.py works as
  expected.

R=davemoore@chromium.org

Review URL: https://codereview.chromium.org/140523003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246649 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 37 insertions, 8 deletions

diff --git a/mojo/public/bindings/generators/template_expander.py b/mojo/public/bindings/generators/template_expander.py
index 41c3cc7..7d56624 100644
--- a/mojo/public/bindings/generators/template_expander.py
+++ b/mojo/public/bindings/generators/template_expander.py
@@ -5,6 +5,7 @@
 # Based on:
 # http://src.chromium.org/viewvc/blink/trunk/Source/build/scripts/template_expander.py
 
+import inspect
 import os
 import sys
 
@@ -20,9 +21,9 @@ sys.path.insert(1, os.path.join(_current_dir,
 import jinja2
 
 
-def ApplyTemplate(path_to_template, params, filters=None):
+def ApplyTemplate(base_dir, path_to_template, params, filters=None):
   template_directory, template_name = os.path.split(path_to_template)
-  path_to_templates = os.path.join(_current_dir, template_directory)
+  path_to_templates = os.path.join(base_dir, template_directory)
   loader = jinja2.FileSystemLoader([path_to_templates])
   jinja_env = jinja2.Environment(loader=loader, keep_trailing_newline=True)
   if filters:
@@ -32,10 +33,13 @@ def ApplyTemplate(path_to_template, params, filters=None):
 
 
 def UseJinja(path_to_template, filters=None):
+  # Get the directory of our caller's file.
+  base_dir = os.path.dirname(inspect.getfile(sys._getframe(1)))
   def RealDecorator(generator):
     def GeneratorInternal(*args, **kwargs):
       parameters = generator(*args, **kwargs)
-      return ApplyTemplate(path_to_template, parameters, filters=filters)
+      return ApplyTemplate(base_dir, path_to_template, parameters,
+                           filters=filters)
     GeneratorInternal.func_name = generator.func_name
     return GeneratorInternal
   return RealDecorator
diff --git a/mojo/public/bindings/mojom_bindings_generator.py b/mojo/public/bindings/mojom_bindings_generator.py
index 91eb501..6f8aea4 100755
--- a/mojo/public/bindings/mojom_bindings_generator.py
+++ b/mojo/public/bindings/mojom_bindings_generator.py
@@ -6,14 +6,34 @@
 """The frontend for the Mojo bindings system."""
 
 
+import imp
 import os
 import sys
 from argparse import ArgumentParser
+from generators import mojom_data
 from parse import mojo_parser
 from parse import mojo_translate
-from generators import mojom_data
-from generators import mojom_cpp_generator
-from generators import mojom_js_generator
+
+
+def LoadGenerators(generators_string):
+  generators = []
+  for generator_name in [s.strip() for s in generators_string.split(",")]:
+    # "Built-in" generators:
+    if generator_name.lower() == "c++":
+      generator_module = __import__("generators.mojom_cpp_generator",
+                                    fromlist=["mojom_cpp_generator"])
+    elif generator_name.lower() == "javascript":
+      generator_module = __import__("generators.mojom_js_generator",
+                                    fromlist=["mojom_js_generator"])
+    # Specified generator python module:
+    elif generator_name.endswith(".py"):
+      generator_module = imp.load_source(os.path.basename(generator_name)[:-3],
+                                         generator_name)
+    else:
+      print "Unknown generator name %s" % generator_name
+      sys.exit(1)
+    generators.append(generator_module)
+  return generators
 
 
 def Main():
@@ -24,11 +44,14 @@ def Main():
                       help="include path for #includes")
   parser.add_argument("-o", "--output_dir", dest="output_dir", default=".",
                       help="output directory for generated files")
+  parser.add_argument("-g", "--generators", dest="generators_string",
+                      metavar="GENERATORS", default="c++,javascript",
+                      help="comma-separated list of generators")
   args = parser.parse_args()
 
   # TODO(vtl): Load these dynamically. (Also add a command-line option to
   # specify which generators.)
-  generator_modules = [mojom_cpp_generator, mojom_js_generator]
+  generator_modules = LoadGenerators(args.generators_string)
 
   if not os.path.exists(args.output_dir):
     os.makedirs(args.output_dir)
@@ -45,6 +68,8 @@ def Main():
                                              args.output_dir)
       generator.GenerateFiles()
 
+  return 0
+
 
 if __name__ == "__main__":
-  Main()
+  sys.exit(Main())