Generate source maps from Closure Compiler

(imported from commit 0e4de860b1dba85aa43b60a2c819ac44403186c5)

humbug/settings.py

@@ -279,8 +279,9 @@ PIPELINE_JS = {
 PIPELINE_CSS_COMPRESSOR = 'pipeline.compressors.yui.YUICompressor'
 PIPELINE_YUI_BINARY     = '/usr/bin/env yui-compressor'
 
-PIPELINE_JS_COMPRESSOR  = 'pipeline.compressors.closure.ClosureCompressor'
+PIPELINE_JS_COMPRESSOR  = 'zephyr.lib.minify.ClosureSourceMapCompressor'
 PIPELINE_CLOSURE_BINARY = os.path.join(SITE_ROOT, '../tools/closure-compiler/run')
+PIPELINE_CLOSURE_SOURCE_MAP_DIR = 'prod-static/source-map'
 
 # Disable stuffing the entire JavaScript codebase inside an anonymous function.
 # We need modules to be externally visible, so that methods can be called from

tools/update-prod-static

@@ -13,6 +13,8 @@ exec >update-prod-static.log
 # running app with PipelineCachedStorage unhappy.  So if you
 # remove a static file, you need to manually remove it from
 # prod-static/collected on the app servers.
+rm -rf prod-static/source-map
+mkdir -p prod-static/source-map
 ./manage.py collectstatic --noinput
 
 # Copy the files we want to expose

zephyr/lib/minify.py

@@ -0,0 +1,19 @@
+from django.conf import settings
+from hashlib     import sha1
+from os          import path
+
+from pipeline.compressors import SubProcessCompressor
+
+class ClosureSourceMapCompressor(SubProcessCompressor):
+    def compress_js(self, js):
+        # js is the full text of the JavaScript source, and we can't
+        # easily get either the input file names or the output file
+        # name.  So we just pick a unique arbitrary name.  This is
+        # okay because we can figure out from the source map file
+        # contents which JavaScript files it corresponds to.
+        source_map = path.join(settings.PIPELINE_CLOSURE_SOURCE_MAP_DIR,
+                               sha1(js).hexdigest() + '.map')
+
+        command = '%s --create_source_map %s' % (
+            settings.PIPELINE_CLOSURE_BINARY, source_map)
+        return self.execute_command(command, js)