fix(mattermost): preserve markdown formatting and native tables (#18655)

Merged via squash.

Prepared head SHA: d30fff1776
Co-authored-by: echo931 <259437483+echo931@users.noreply.github.com>
Co-authored-by: mukhtharcm <56378562+mukhtharcm@users.noreply.github.com>
Reviewed-by: @mukhtharcm

extensions/mattermost/src/mattermost/monitor-helpers.test.ts

@@ -0,0 +1,82 @@
+import { describe, expect, it } from "vitest";
+import { normalizeMention } from "./monitor-helpers.js";
+
+describe("normalizeMention", () => {
+  it("returns trimmed text when no mention provided", () => {
+    expect(normalizeMention("  hello world  ", undefined)).toBe("hello world");
+  });
+
+  it("strips bot mention from text", () => {
+    expect(normalizeMention("@echobot hello", "echobot")).toBe("hello");
+  });
+
+  it("strips mention case-insensitively", () => {
+    expect(normalizeMention("@EchoBot hello", "echobot")).toBe("hello");
+  });
+
+  it("preserves newlines in multi-line messages", () => {
+    const input = "@echobot\nline1\nline2\nline3";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toBe("line1\nline2\nline3");
+  });
+
+  it("preserves Markdown headings", () => {
+    const input = "@echobot\n# Heading\n\nSome text";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toContain("# Heading");
+    expect(result).toContain("\n");
+  });
+
+  it("preserves Markdown blockquotes", () => {
+    const input = "@echobot\n> quoted line\n> second line";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toContain("> quoted line");
+    expect(result).toContain("> second line");
+  });
+
+  it("preserves Markdown lists", () => {
+    const input = "@echobot\n- item A\n- item B\n  - sub B1";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toContain("- item A");
+    expect(result).toContain("- item B");
+  });
+
+  it("preserves task lists", () => {
+    const input = "@echobot\n- [ ] todo\n- [x] done";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toContain("- [ ] todo");
+    expect(result).toContain("- [x] done");
+  });
+
+  it("handles mention in middle of text", () => {
+    const input = "hey @echobot check this\nout";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toBe("hey check this\nout");
+  });
+
+  it("preserves leading indentation for nested lists", () => {
+    const input = "@echobot\n- item\n  - nested\n    - deep";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toContain("  - nested");
+    expect(result).toContain("    - deep");
+  });
+
+  it("preserves first-line indentation for nested list items", () => {
+    const input = "@echobot\n  - nested\n    - deep";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toBe("  - nested\n    - deep");
+  });
+
+  it("preserves indented code blocks", () => {
+    const input = "@echobot\ntext\n    code line 1\n    code line 2";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toContain("    code line 1");
+    expect(result).toContain("    code line 2");
+  });
+
+  it("preserves first-line indentation for indented code blocks", () => {
+    const input = "@echobot\n    code line 1\n    code line 2";
+    const result = normalizeMention(input, "echobot");
+    expect(result).toBe("    code line 1\n    code line 2");
+  });
+});

extensions/mattermost/src/mattermost/monitor-helpers.ts

@@ -70,3 +70,38 @@ export function resolveThreadSessionKeys(params: {
     normalizeThreadId: (threadId) => threadId,
   });
 }
+
+/**
+ * Strip bot mention from message text while preserving newlines and
+ * block-level Markdown formatting (headings, lists, blockquotes).
+ */
+export function normalizeMention(text: string, mention: string | undefined): string {
+  if (!mention) {
+    return text.trim();
+  }
+  const escaped = mention.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+  const hasMentionRe = new RegExp(`@${escaped}\\b`, "i");
+  const leadingMentionRe = new RegExp(`^([\\t ]*)@${escaped}\\b[\\t ]*`, "i");
+  const trailingMentionRe = new RegExp(`[\\t ]*@${escaped}\\b[\\t ]*$`, "i");
+  const normalizedLines = text.split("\n").map((line) => {
+    const hadMention = hasMentionRe.test(line);
+    const normalizedLine = line
+      .replace(leadingMentionRe, "$1")
+      .replace(trailingMentionRe, "")
+      .replace(new RegExp(`@${escaped}\\b`, "gi"), "")
+      .replace(/(\S)[ \t]{2,}/g, "$1 ");
+    return {
+      text: normalizedLine,
+      mentionOnlyBlank: hadMention && normalizedLine.trim() === "",
+    };
+  });
+
+  while (normalizedLines[0]?.mentionOnlyBlank) {
+    normalizedLines.shift();
+  }
+  while (normalizedLines.at(-1)?.text.trim() === "") {
+    normalizedLines.pop();
+  }
+
+  return normalizedLines.map((line) => line.text).join("\n");
+}

extensions/mattermost/src/mattermost/monitor.ts

@@ -70,6 +70,7 @@ import {
 import {
   createDedupeCache,
   formatInboundFromLabel,
+  normalizeMention,
   resolveThreadSessionKeys,
 } from "./monitor-helpers.js";
 import { resolveOncharPrefixes, stripOncharPrefix } from "./monitor-onchar.js";
@@ -143,15 +144,6 @@ function resolveRuntime(opts: MonitorMattermostOpts): RuntimeEnv {
   );
 }
 
-function normalizeMention(text: string, mention: string | undefined): string {
-  if (!mention) {
-    return text.trim();
-  }
-  const escaped = mention.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
-  const re = new RegExp(`@${escaped}\\b`, "gi");
-  return text.replace(re, " ").replace(/\s+/g, " ").trim();
-}
-
 function isSystemPost(post: MattermostPost): boolean {
   const type = post.type?.trim();
   return Boolean(type);