Fix placeholder syntax for Chrome extensions.

grit/format/chrome_messages_json.py

Index: grit/format/chrome_messages_json.py
diff --git a/grit/format/chrome_messages_json.py b/grit/format/chrome_messages_json.py
index be934ab1175924657a79796dbf0def4c2464ec5f..7cd0e28b98d9bb6dfa24355c7a901c42531deb4e 100644
--- a/grit/format/chrome_messages_json.py
+++ b/grit/format/chrome_messages_json.py
@@ -19,8 +19,11 @@ def Format(root, lang='en', output_dir='.'):
 
   encoder = JSONEncoder();
   format = ('  "%s": {\n'
-            '    "message": %s\n'
+            '    "message": %s\n%s'
             '  }')
+  placeholder_format = ('    "%i": {\n'

[kelvinp, 2015/11/04 19:02:10]

According to the documentation, the placeholder is optional.  I wonder if there
is much value in generating placeholder that only have

1: {
  content: "$1
}

There may be more value in parsing the <ph> tag and fill in the example value.

[kelvinp, 2015/11/04 19:09:04]

Spoke with Jamie offline.  We want to minimize text in an output file.

[Jamie, 2015/11/04 19:13:55]

It's only optional insofar as you don't need it for messages with no
placeholders that use the $name$ syntax. Since we are using that syntax, we need
it.
I considered that, but since the messages.json files are output files (ie, not
intended to be human-readable), there's not a lot of value in copying that
information across. It would also make the code more complex.

+                        '      "content": "$%i"\n'
+                        '    }')
   first = True
   for child in root.ActiveDescendants():
     if isinstance(child, message.MessageNode):
@@ -31,9 +34,23 @@ def Format(root, lang='en', output_dir='.'):
       loc_message = encoder.encode(child.ws_at_start + child.Translate(lang) +
                                    child.ws_at_end)
 
+      # Replace $n place-holders with $n$ and add an appropriate "placeholders"
+      # entry.
+      placeholders = ''
+      for i in range(1, 10):

[kelvinp, 2015/11/04 19:02:10]

Is 10 the maximum number of placeholders?
Nevermind, found the information on
https://developer.chrome.com/extensions/i18n#method-getMessage
There can only be 9 substitution strings.

[kelvinp, 2015/11/04 19:09:04]

May be good to include the link about there can only be 9 parameters in the
comment.

[Jamie, 2015/11/04 19:13:55]

Acknowledged.

+        if loc_message.find('$%d' % i) == -1:
+          break
+        loc_message = loc_message.replace('$%d' % i, '$%d$' % i)
+        if placeholders:
+          placeholders += ',\n'
+        placeholders += placeholder_format % (i, i)
+
       if not first:
         yield ',\n'
       first = False
-      yield format % (id, loc_message)
+
+      if placeholders:
+        placeholders = ',\n  "placeholders": {\n%s\n  }' % placeholders
+      yield format % (id, loc_message, placeholders)
 
   yield '\n}\n'