composebox_typeahead: Avoid generating broken links. #30071

kuv2707 · 2024-05-13T09:28:54Z

The #**stream>topic** syntax generates broken links for topics containing two backticks or starting/ending with *, because of architectural flaws in the backend markdown processor. So we avoid generating the syntax for such topics and instead generate the normal link syntax in markdown.

Fixes #19873

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kuv2707

I have made a preliminary implementation and highlighted the reasons behind some technical choices.
Once we decide the correct logic to detect faulty topic names, I'll refactor the functions and put them in a sensible place.

kuv2707 · 2024-05-13T09:35:53Z

web/src/composebox_typeahead.js

@@ -995,8 +997,29 @@ export function content_typeahead_selected(item, query, input_element, event) {
            // Stream + topic mention typeahead; close the stream+topic mention syntax
            // with the topic and the final **.  Note that token.length can be 0
            // if we are completing from `**streamname>`.
+            function will_produce_broken_link(topic) {


Currently, I have considered only two cases which produced buggy links:

When there are two or more backticks

When the topic name begins or ends with asterisks.

There can still be topic names which cause broken links. I had earlier tried to parse the syntax text using the frontend markdown parser and see if the link in the parsed html points to the correct stream and topic. But double-backtick topic names gave different urls through frontend and backend markdown processors (in fact, the frontend parser correctly parsed the double-backtick topic name, while the backend processor generated an incorrect url).

This means that checking if the frontend markdown processor parses the syntax correctly gives no guarantee about the correctness of the link in the final message. So I thought the best option would be to check for the individual reported cases which produce broken urls.

I infer from CZO discussions that we will eventually move to a different markdown processor, and this will no longer be an issue then.

web/src/composebox_typeahead.js

alya · 2024-05-14T22:09:44Z

@timabbott Do you want to take a look and provide some feedback here?

timabbott · 2024-05-17T17:54:53Z

web/src/composebox_typeahead.ts

+                    beginning.slice(0, syntax_start_index) +
+                    url_syntax(get_stream_name(beginning), item.topic) +
+                    " ";
+            }


Can you extract this logic to a function and/or add unit tests for it? It's complicated enough that it's very much worth having a test for.

I have extracted the logic and added some unit tests.

kuv2707 · 2024-05-20T08:34:57Z

@timabbott Addressed the suggestion. Please take a look.

timabbott · 2024-05-20T16:40:28Z

web/tests/composebox_typeahead.test.js

+    );
+    assert.equal(
+        ct.stream_topic_link_syntax("#**stream>t", "*asterisk"),
+        "[#stream>*asterisk](#narrow/stream/-1-unknown/topic/*asterisk) ",


Why do all of these have -1 as the stream ID in the URLs? The first couple don't, which makes me think you've got some sort of weird bug in either one test case or the other.

stream ids are only required when we generate the markdown link syntax (since we need to generate the url ourselves).
That is why the first two didn't need them.

timabbott · 2024-05-20T16:40:55Z

web/tests/composebox_typeahead.test.js

+            stream_topic_hash: hash_util.by_stream_topic_url,
+            get_stream_by_name() {
+                return "Rome";
+            },


This mock seems unnecessary; can't we just use add the stream to the stream_data database and avoid the hackery?

Sure, I was trying to mimic the code path followed by the frontend markdown processor (which uses markdown_config.ts), which in retrospect, seems unnecessary.

I have removed these and used the streams already present for the tests. This simplified the code a lot.

kuv2707 · 2024-05-20T17:57:40Z

web/src/composebox_typeahead.ts

@@ -1180,6 +1185,31 @@ export function content_typeahead_selected(
    return beginning + rest;
 }

+function will_produce_broken_stream_topic_link(topic_name: string): boolean {
+    return /(\*+)|(.*`.*`.*)/.test(topic_name);


The links for topic names with double backticks are now generated correctly, but the double backticks cause the enclosed part of the topic name to render as an inline code block.
I don't know what to do in this case since backslash escaping is disabled.

The #**stream>topic** syntax generates broken links for topics containing two backticks or ending with *, because of architectural flaws in the backend markdown processor. So we avoid generating the syntax for such topics and instead generate the normal link syntax in markdown. Fixes zulip#19873

zulipbot added size: S area: markdown (mentions) Mentions for users/groups/stream/topic/time. bug rust community request Issues of interest to the Rust community labels May 13, 2024

kuv2707 commented May 13, 2024

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kuv2707 mentioned this pull request May 14, 2024

Compose Box: Implement formatting of channels and topics on paste #29302

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alya added the integration review Added by maintainers when a PR may be ready for integration. label May 14, 2024

kuv2707 force-pushed the 19873_topic_name_fix branch from 07cab3f to dbcdfa0 Compare May 17, 2024 10:16

timabbott reviewed May 17, 2024

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kuv2707 force-pushed the 19873_topic_name_fix branch from dbcdfa0 to 0a026be Compare May 18, 2024 16:11

zulipbot added size: L and removed size: S labels May 18, 2024

kuv2707 force-pushed the 19873_topic_name_fix branch from 0a026be to ff0ba14 Compare May 20, 2024 08:07

kuv2707 requested a review from timabbott May 20, 2024 08:33

kuv2707 force-pushed the 19873_topic_name_fix branch from ff0ba14 to 7455824 Compare May 20, 2024 08:55

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kuv2707 commented May 20, 2024

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kuv2707 force-pushed the 19873_topic_name_fix branch from 7455824 to a3c5613 Compare May 20, 2024 18:04

kuv2707 force-pushed the 19873_topic_name_fix branch from a3c5613 to 8c243b1 Compare May 21, 2024 12:16

kuv2707 requested a review from timabbott May 21, 2024 15:38

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composebox_typeahead: Avoid generating broken links. #30071

composebox_typeahead: Avoid generating broken links. #30071

kuv2707 commented May 13, 2024 •

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composebox_typeahead: Avoid generating broken links. #30071

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composebox_typeahead: Avoid generating broken links. #30071

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