Bug 1172800 - Avoid using inspect.getsourcelines() and inspect.getfile(). r=gps

inspect.getsourcelines() and inspect.getfile() involve I/O out of our control.
Our use of those functions, however, doesn't require all their smarts. In fact,
we only use them on function objects, for which we can just do the work
ourselves without involving inspect functions that trigger I/O.

python/mozbuild/mozbuild/frontend/reader.py

@@ -324,7 +324,7 @@ class MozbuildSandbox(Sandbox):
         if name.islower() or name.isupper() or name[0].islower():
             raise NameError('Template function names must be CamelCase.')
 
-        self.templates[name] = TemplateFunction(func)
+        self.templates[name] = TemplateFunction(func, self)
 
     @memoize
     def _create_subcontext(self, cls):
@@ -408,11 +408,13 @@ class MozbuildSandbox(Sandbox):
 
 
 class TemplateFunction(object):
-    def __init__(self, func):
-        self.path = inspect.getfile(func)
+    def __init__(self, func, sandbox):
+        self.path = func.func_code.co_filename
         self.name = func.func_name
 
-        lines, firstlineno = inspect.getsourcelines(func)
+        firstlineno = func.func_code.co_firstlineno
+        lines = sandbox._current_source.splitlines(True)
+        lines = inspect.getblock(lines[firstlineno - 1:])
         first_op = None
         generator = tokenize.generate_tokens(iter(lines).next)
         # Find the first indent token in the source of this template function,

python/mozbuild/mozbuild/frontend/sandbox.py

@@ -129,6 +129,9 @@ class Sandbox(dict):
         # evaluation.
         self._last_name_error = None
 
+        # Current literal source being executed.
+        self._current_source = None
+
     @property
     def _context(self):
         return self._active_contexts[-1]
@@ -171,6 +174,8 @@ class Sandbox(dict):
         # too low-level for that. However, we could add bytecode generation via
         # the marshall module if parsing performance were ever an issue.
 
+        old_source = self._current_source
+        self._current_source = source
         try:
             # compile() inherits the __future__ from the module by default. We
             # do want Unicode literals.
@@ -212,6 +217,7 @@ class Sandbox(dict):
                 source_stack.append(path)
             raise SandboxExecutionError(source_stack, exc[0], exc[1], exc[2])
         finally:
+            self._current_source = old_source
             self._context._sandbox = old_sandbox
             if path and becomes_current_path:
                 self._context.pop_source()