Add Approved and Delegated structured comments

Sometimes, Homu will leave an unstructured comment on a pull request,
like:

    :emoji: Something happened!

Other times, Homu will leave a structured comment, which is some text
followed by a hidden JSON blob, like:

    :emoji: Something happened!

    <!-- homu: {"type":"SomethingHappened","arg1":"value"} -->

This commit converts the "approved", "delegated", and "approval ignored
because the pull request is a WIP" messages from unstructured to
structured.

Having more of our comments be structured may help us perform better
startup synchronization in the future, because we can better inspect
what Homu thought its state was before it was restarted.

Author: bryanburgers

homu/comments.py

@@ -18,6 +18,58 @@ def jsonify(self):
         return json.dumps(out, separators=(',', ':'))
 
 
+class Approved(Comment):
+    def __init__(self, bot=None, **args):
+        # Because homu needs to leave a comment for itself to kick off a build,
+        # we need to know the correct botname to use. However, we don't want to
+        # save that botname in our state JSON. So we need a custom constructor
+        # to grab the botname and delegate the rest of the keyword args to the
+        # Comment constructor.
+        super().__init__(**args)
+        self.bot = bot
+
+    params = ["sha", "approver"]
+
+    def render(self):
+        # The comment here is apparently required because Homu seems to use
+        # this note-to-self comment to kick off the build. Presumably because
+        # it contains the full commit hash?
+        message = ":pushpin: Commit {sha} has been " + \
+            "approved by `{approver}`\n\n" + \
+            "<!-- @{bot} r={approver} {sha} -->"
+        return message.format(
+            sha=self.sha,
+            approver=self.approver,
+            bot=self.bot
+        )
+
+
+class ApprovalIgnoredWip(Comment):
+    def __init__(self, wip_keyword=None, **args):
+        # We want to use the wip keyword in the message, but not in the json
+        # blob.
+        super().__init__(**args)
+        self.wip_keyword = wip_keyword
+
+    params = ["sha"]
+
+    def render(self):
+        message = ':clipboard:' + \
+            ' Looks like this PR is still in progress,' + \
+            ' ignoring approval.\n\n' + \
+            'Hint: Remove **{wip_keyword}** from this PR\'s title when' + \
+            ' it is ready for review.'
+        return message.format(wip_keyword=self.wip_keyword)
+
+
+class Delegated(Comment):
+    params = ["delegator", "delegate"]
+
+    def render(self):
+        message = ':v: @{} can now approve this pull request'
+        return message.format(self.delegate)
+
+
 class BuildStarted(Comment):
     params = ["head_sha", "merge_sha"]
 

homu/main.py

@@ -497,13 +497,10 @@ def parse_commands(body, username, repo_label, repo_cfg, state, my_username,
             for wip_kw in ['WIP', 'TODO', '[WIP]', '[TODO]', '[DO NOT MERGE]']:
                 if state.title.upper().startswith(wip_kw):
                     if realtime:
-                        state.add_comment((
-                            ':clipboard:'
-                            ' Looks like this PR is still in progress,'
-                            ' ignoring approval.\n\n'
-                            'Hint: Remove **{}** from this PR\'s title when'
-                            ' it is ready for review.'
-                        ).format(wip_kw))
+                        state.add_comment(comments.ApprovalIgnoredWip(
+                            sha=state.head_sha,
+                            wip_keyword=wip_kw,
+                        ))
                     is_wip = True
                     break
             if is_wip:
@@ -565,14 +562,10 @@ def parse_commands(body, username, repo_label, repo_cfg, state, my_username,
                         .format(msg, state.head_sha)
                     )
                 else:
-                    state.add_comment(
-                        ':pushpin: Commit {} has been approved by `{}`\n\n<!-- @{} r={} {} -->'  # noqa
-                        .format(
-                            state.head_sha,
-                            approver,
-                            my_username,
-                            approver,
-                            state.head_sha,
+                    state.add_comment(comments.Approved(
+                        sha=state.head_sha,
+                        approver=approver,
+                        bot=my_username,
                     ))
                     treeclosed = state.blocked_by_closed_tree()
                     if treeclosed:
@@ -620,10 +613,10 @@ def parse_commands(body, username, repo_label, repo_cfg, state, my_username,
             state.save()
 
             if realtime:
-                state.add_comment(
-                    ':v: @{} can now approve this pull request'
-                    .format(state.delegate)
-                )
+                state.add_comment(comments.Delegated(
+                    delegator=username,
+                    delegate=state.delegate
+                ))
 
         elif word == 'delegate-':
             # TODO: why is this a TRY?
@@ -640,10 +633,10 @@ def parse_commands(body, username, repo_label, repo_cfg, state, my_username,
             state.save()
 
             if realtime:
-                state.add_comment(
-                    ':v: @{} can now approve this pull request'
-                    .format(state.delegate)
-                )
+                state.add_comment(comments.Delegated(
+                    delegator=username,
+                    delegate=state.delegate
+                ))
 
         elif word == 'retry' and realtime:
             if not _try_auth_verified():