collectstatic improvements.

bin/steps/collectstatic

 #!/usr/bin/env bash
 
+# Django Collectstatic runner. If you have Django installed, collectstatic will
+# automatically be executed as part of the build process. If collectstatic
+# fails, your build fails.
+
+# This functionality will only activate if Django is in requirements.txt.
+
+# Runtime arguments:
+#   - $DISABLE_COLLECTSTATIC: disables this functionality.
+#   - $DEBUG_COLLECTSTATIC: upon failure, print out environment variables.
+
 source $BIN_DIR/utils
 
+# Location of 'manage.py', if it exists.
 MANAGE_FILE=$(find . -maxdepth 3 -type f -name 'manage.py' -printf '%d\t%P\n' | sort -nk1 | cut -f2 | head -1)
 MANAGE_FILE=${MANAGE_FILE:-fakepath}
 
+# Legacy file-based support for $DISABLE_COLLECTSTATIC
 [ -f .heroku/collectstatic_disabled ] && DISABLE_COLLECTSTATIC=1
+
+# Ensure that Django is explicitily specified in requirments.txt
 pip-grep -s requirements.txt django Django && DJANGO_INSTALLED=1
 
-bpwatch start collectstatic
+bpwatch start collectstatic  # metrics collection
 
 if [ ! "$DISABLE_COLLECTSTATIC" ] && [ -f "$MANAGE_FILE" ] && [ "$DJANGO_INSTALLED" ]; then
     set +e
 
     echo "-----> Preparing static assets with 'collectstatic'."
 
-    echo "       Running collectstatic..."
+    # Run collectstatic, cleanup some of the noisy output.
     python $MANAGE_FILE collectstatic --noinput  2>&1 | sed '/^Copying/d;/^$/d;/^ /d' | indent
 
     # Display a warning if collectstatic failed.
@@ -23,6 +37,16 @@ if [ ! "$DISABLE_COLLECTSTATIC" ] && [ -f "$MANAGE_FILE" ] && [ "$DJANGO_INSTALL
         echo " !     Error while runnning '$ python $MANAGE_FILE collectstatic --noinput'."
         echo "       See traceback above for more details."
         echo "       More info: http://devcenter.heroku.com/articles/django-assets"
+
+        # Additionally, dump out the environment, if debug mode is on.
+        if [ "$DEBUG_COLLECTSTATIC" ]; then
+            echo
+            echo "****** Collectstatic environment variables:"
+            echo
+            env
+        fi
+
+        # Abort the build.
         exit 1
     }
 
@@ -30,4 +54,4 @@ if [ ! "$DISABLE_COLLECTSTATIC" ] && [ -f "$MANAGE_FILE" ] && [ "$DJANGO_INSTALL
     echo
 fi
 
-bpwatch stop collectstatic
+bpwatch stop collectstatic  # metrics collection