commit 6c215337b4e612d3a40ce14a1a266677d580aa5e
author Edwin Kempin <ekempin@google.com> Tue Nov 22 08:06:34 2022 +0100
committer Edwin Kempin <ekempin@google.com> Thu Nov 24 14:23:02 2022 +0100
tree f2814066fea9760b34c6fd307119a8a7d6f15ba8
parent 0e5417ad2f24b40e03bb6c4d45b83fefc307d627

Highlight matching atoms of copy conditions in change messages

When a new patch set is created and approvals are copied to the new
patch set or if approvals are dropped (because they cannot be copied to
the new patch set) Gerrit posts a change message to inform about the
copied and outdated votes. For each copied/outdated vote the change
message includes the corresponding copy condition, so that users can
check why a vote matched or didn't match the copy condition.

Understanding why a vote matched or didn't match the copy condition
could be easier though if the passing and failing atoms in the copy
condition would be highlighted. E.g. for expressions of submit
requirements we already have such highlighting (passing atoms are
underlined in green, failing atoms are underlined in red).

It would be nice to have the same highlighting for copy conditions, but
it's not easily doable. For the expressions of the submit requirements
the highlighting is done in the web frontend. This requires the web
frontend to know about the expression and the passing and failing atoms,
which means that the backend must have an API to return this data.
Adding such an API for copy conditions is not easy, since they are
embedded in change messages which are plain strings. In addition the
backend has only the current copy condition available and in restrospect
it can't tell how the copy condition looked like at the moment when the
copy evaluation for a certain approval was done.

That's why for highlighting atoms in copy conditions we take a different
approach. The change message with the copy conditions is generated at
the moment when the copy evaluation is done. At this moment we can check
which atoms of the copy conditions are passing/failing. We can then use
this information to highlight the passing atoms in the change message.
The change message is a plain string, but Markdown formatting is
supported. We make use of this and use Markdown syntax to print passing
atoms in bold. This is not the same formatting as for expressions of
submit requirements, but it's the best we can do with Markdown. Markdown
does neither support underlining text nor colored text (this is only
possible with HTML snippets but those are not supported in change
messages). This approach can be implemented with little effort and still
allows us to highlight which atoms of a copy condition are passing.

To implement this we compute the passing/failing atoms of the copy
condition at the moment when the copy evaluation in ApprovalCopier is
done. To pass this information to the caller we change the type for the
copied/outdated approvals in ApprovalCopier.Result from PatchSetApproval
to a new ApprovalData type that contains the PatchSetApproval and the
passing and failing atoms (for consistency the method names for getting
the passing/failing atoms are kept the same as for
SubmitRequirementExpressionResult).

ApprovalsUtil gets the copied/outdated approvals as input to format the
change message with copied/dropped votes. In addition to the
copied/outdated approvals it now has the passing and failing atoms
available for each approval, so that it can format the passing atoms in
bold (using Markdown syntax).

So far approvals with the same label had been grouped as one line in the
change message (since they have the same copy condition), e.g.:

  Copied Votes:
  * Code-Review-2, Code-Review+2 (copy condition: "is:MIN OR is:MAX")

Now we need to split those into multiple lines if the passing atoms
differ, so that in every line we can higlight different atoms:

 Copied Votes:
  * Code-Review-2 (copy condition: "**is:MIN** OR is:MAX")
  * Code-Review+2 (copy condition: "is:MIN OR **is:MAX**")

If approvals for the same label have the same passing atoms they are
still grouped together as one line, e.g.:

  Copied Votes:
  * Code-Review-1, Code-Review+1 (copy condition: "is:MIN OR **changekind:TRIVIAL_REBASE**")

Bug: Google b/240377462
Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I7b42f350f9d79b1dc3cac62aeac7d7c7f8699456
Release-Notes: Matching atoms in copy conditions that are posted as change messages are highlighted in bold now