Add tests for :bug

These exposed a few issues with the output formatting, so those are also
addressed here.

unison-cli/src/Unison/Codebase/Transcript/Runner.hs

@@ -210,18 +210,19 @@ run isTest verbosity dir codebase runtime sbRuntime nRuntime ucmVersion baseURL
         liftIO $ writeIORef hasErrors True
         liftIO (liftA2 (,) (readIORef allowErrors) (readIORef expectFailure)) >>= \case
           (False, False) -> liftIO . dieWithMsg $ Pretty.toPlain terminalWidth msg
-          (True, True) ->
-            transcriptFailure
-              out
-              ( Text.pack . Pretty.toPlain terminalWidth $
-                  Pretty.lines
-                    [ "The stanza above marked with `:error :bug` is now failing with",
-                      Pretty.border 2 msg,
-                      "so you can remove `:bug` and close any appropriate Github issues. If the error message is \
-                      \different from the expected error message, open a new issue and reference it in this transcript."
-                    ]
-              )
-              Nothing
+          (True, True) -> do
+            appendFailingStanza
+            fixedBug out $
+              Text.unlines
+                [ "The stanza above marked with `:error :bug` is now failing with",
+                  "",
+                  "```",
+                  Text.pack $ Pretty.toPlain terminalWidth msg,
+                  "```",
+                  "",
+                  "so you can remove `:bug` and close any appropriate Github issues. If the error message is different \
+                  \from the expected error message, open a new issue and reference it in this transcript."
+                ]
           (_, _) -> pure ()
 
       apiRequest :: APIRequest -> IO [APIRequest]
@@ -467,12 +468,10 @@ run isTest verbosity dir codebase runtime sbRuntime nRuntime ucmVersion baseURL
               "The transcript was expecting an error in the stanza above, but did not encounter one."
               Nothing
           (False, True, False) -> do
-            appendFailingStanza
-            transcriptFailure
+            fixedBug
               out
               "The stanza above with `:bug` is now passing! You can remove `:bug` and close any appropriate Github \
               \issues."
-              Nothing
           (_, _, _) -> pure ()
 
   authenticatedHTTPClient <- AuthN.newAuthenticatedHTTPClient tokenProvider ucmVersion
@@ -528,6 +527,22 @@ transcriptFailure out heading mbody = do
               <> foldr ((:) . CMarkCodeBlock Nothing "") [] mbody
         )
 
+fixedBug :: IORef (Seq Stanza) -> Text -> IO b
+fixedBug out body = do
+  texts <- readIORef out
+  -- `CMark.commonmarkToNode` returns a @DOCUMENT@, which won’t be rendered inside another document, so we strip the
+  -- outer `CMark.Node`.
+  let CMark.Node _ _DOCUMENT bodyNodes = CMark.commonmarkToNode [CMark.optNormalize] body
+  UnliftIO.throwIO . RunFailure $
+    texts
+      <> Seq.fromList
+        ( Left
+            <$> [ CMark.Node Nothing CMark.PARAGRAPH [CMark.Node Nothing (CMark.TEXT "🎉") []],
+                  CMark.Node Nothing (CMark.HEADING 2) [CMark.Node Nothing (CMark.TEXT "You fixed a bug!") []]
+                ]
+              <> bodyNodes
+        )
+
 data Error
   = ParseError (P.ParseErrorBundle Text Void)
   | RunFailure (Seq Stanza)

unison-src/transcripts/errors/obsolete-bug.md

@@ -0,0 +1,5 @@
+This transcript will error, because we’re claiming that the stanza has a bug, but `help` works as expected.
+
+``` ucm :bug
+scratch/main> help edit
+```

unison-src/transcripts/errors/obsolete-bug.output.md

@@ -0,0 +1,15 @@
+This transcript will error, because we’re claiming that the stanza has a bug, but `help` works as expected.
+
+``` ucm :bug
+scratch/main> help edit
+
+  edit
+  `edit foo` prepends the definition of `foo` to the top of the most recently saved file.
+  `edit` without arguments invokes a search to select a definition for editing, which requires that `fzf` can be found within your PATH.
+```
+
+🎉
+
+## You fixed a bug\!
+
+The stanza above with `:bug` is now passing\! You can remove `:bug` and close any appropriate Github issues.

unison-src/transcripts/errors/obsolete-error-bug.md

@@ -0,0 +1,5 @@
+This transcript will fail, because we’re claiming that the stanza has a bug, but `do.something` errors as expected.
+
+``` ucm :error :bug
+scratch/main> do.something
+```

unison-src/transcripts/errors/obsolete-error-bug.output.md

@@ -0,0 +1,19 @@
+This transcript will fail, because we’re claiming that the stanza has a bug, but `do.something` errors as expected.
+
+``` ucm :error :bug
+scratch/main> do.something
+```
+
+🎉
+
+## You fixed a bug\!
+
+The stanza above marked with `:error :bug` is now failing with
+
+``` 
+⚠️
+I don't know how to do.something. Type `help` or `?` to get
+help.
+```
+
+so you can remove `:bug` and close any appropriate Github issues. If the error message is different from the expected error message, open a new issue and reference it in this transcript.

unison-src/transcripts/idempotent/bug.md

@@ -0,0 +1,19 @@
+This tests that `:bug` behaves similarly to `:error` when the stanza fails.
+
+``` ucm :bug
+scratch/main> do.something
+
+  ⚠️
+  I don't know how to do.something. Type `help` or `?` to get
+  help.
+```
+
+And when combined with `:error`, it should expect a successful result.
+
+``` ucm :error :bug
+scratch/main> help edit
+
+  edit
+  `edit foo` prepends the definition of `foo` to the top of the most recently saved file.
+  `edit` without arguments invokes a search to select a definition for editing, which requires that `fzf` can be found within your PATH.
+```