Die build.py, Die: Part 2 (LocalFetcher, Handlebar support, build script)

chrome/common/extensions/docs/server2/template_fetcher.py

+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import logging
+import os
+import time
+
+from third_party.handlebar import Handlebar
+
+# Cache templates for 5 minutes.
+CACHE_TIMEOUT = 300
+
+# Cached templates stored as (branch, path) -> (template, cache time)
+# The template cache is global so it will not be erased each time a new
+# TemplateFetcher is created.
+TEMPLATE_CACHE = {}
+
+class TemplateFetcher(object):
+  def __init__(self, branch, fetcher):
+    self._fetcher = fetcher
+    self._branch = branch
+
+  def __getitem__(self, key):
+    if (self._branch, key) not in TEMPLATE_CACHE:

[Aaron Boodman, 2012/06/05 00:50:04]

Nit: Is there a reason for FetchTemplate() now? It seems like all hte logic
could move here.

[not at google - send to devlin, 2012/06/05 00:56:10]

Python style guide reasons?

[cduvall, 2012/06/05 01:07:37]

I moved it for now we can move it back out to FetchTemplate if it gets too big.

+      self.FetchTemplate(key)
+    return TEMPLATE_CACHE[(self._branch, key)][0]
+
+  def FetchTemplate(self, path):
+    key = (self._branch, path)
+    # Check the template cache and whether the cache has expired.
+    if key in TEMPLATE_CACHE:
+      if TEMPLATE_CACHE[key][1] < CACHE_TIMEOUT:

[Aaron Boodman, 2012/06/05 00:50:04]

Indexing tuples by number like this always looks ugly to me. Better to get the
values out, like:

template, cache_time = TEMPLATE_CACHE[key]
if (cache_time < ...)

[Aaron Boodman, 2012/06/05 00:50:04]

Does this work? Seems like you need to subtract from now.

[Aaron Boodman, 2012/06/05 00:50:04]

kalman is right that this is going to be a pain especially when working locally.

I think that in a future CL, you should expose the amount of time to cache as a
property of this class, and set it to zero in the local case.

[cduvall, 2012/06/05 01:07:37]

Done.

[cduvall, 2012/06/05 01:07:37]

Done.

[cduvall, 2012/06/05 01:07:37]

Agreed, I'll do that in the next CL.

+        return TEMPLATE_CACHE[key][0]
+    logging.info('Template cache miss for: ' + path)
+    template = self._fetcher.FetchResource(self._branch, path).content
+    compiled_template = Handlebar(template)
+    TEMPLATE_CACHE[key] = (compiled_template, time.clock())
+    return compiled_template