DEV: allows chat to render specific html tags (#26591)

This commit adds two custom markdown rules:
- chat-html-block
- chat-html-inline

For now it only allows `<kbd>` for inline and `<details>` for block.

plugins/chat/assets/javascripts/lib/discourse-markdown/chat-html-block.js

@@ -0,0 +1,114 @@
+// inspired from https://github.com/markdown-it/markdown-it/blob/master/lib/rules_block/html_block.mjs
+// note that allow lister will run on top of it, so if a tag is allowed here but not on
+// the allow list, then it won't show up
+
+const block_names = ["details"];
+
+const attr_name = "[a-zA-Z_:][a-zA-Z0-9:._-]*";
+const unquoted = "[^\"'=<>`\\x00-\\x20]+";
+const single_quoted = "'[^']*'";
+const double_quoted = '"[^"]*"';
+const attr_value =
+  "(?:" + unquoted + "|" + single_quoted + "|" + double_quoted + ")";
+const attribute = "(?:\\s+" + attr_name + "(?:\\s*=\\s*" + attr_value + ")?)";
+const open_tag = "<[A-Za-z][A-Za-z0-9\\-]*" + attribute + "*\\s*\\/?>";
+const close_tag = "<\\/[A-Za-z][A-Za-z0-9\\-]*\\s*>";
+
+const HTML_OPEN_CLOSE_TAG_RE = new RegExp(
+  "^(?:" + open_tag + "|" + close_tag + ")"
+);
+
+// An array of opening and corresponding closing sequences for html tags,
+// last argument defines whether it can terminate a paragraph or not
+//
+const HTML_SEQUENCES = [
+  [
+    /^<(script|pre|style|textarea)(?=(\s|>|$))/i,
+    /<\/(script|pre|style|textarea)>/i,
+    true,
+  ],
+  [/^<!--/, /-->/, true],
+  [/^<\?/, /\?>/, true],
+  [/^<![A-Z]/, />/, true],
+  [/^<!\[CDATA\[/, /\]\]>/, true],
+  [
+    new RegExp("^</?(" + block_names.join("|") + ")(?=(\\s|/?>|$))", "i"),
+    /^$/,
+    true,
+  ],
+  [new RegExp(HTML_OPEN_CLOSE_TAG_RE.source + "\\s*$"), /^$/, false],
+];
+
+function chatHtmlBlock(state, startLine, endLine, silent) {
+  let pos = state.bMarks[startLine] + state.tShift[startLine];
+  let max = state.eMarks[startLine];
+
+  // if it's indented more than 3 spaces, it should be a code block
+  if (state.sCount[startLine] - state.blkIndent >= 4) {
+    return false;
+  }
+
+  if (!state.md.options.html) {
+    return false;
+  }
+
+  if (state.src.charCodeAt(pos) !== 0x3c /* < */) {
+    return false;
+  }
+
+  let lineText = state.src.slice(pos, max);
+
+  let i = 0;
+  for (; i < HTML_SEQUENCES.length; i++) {
+    if (HTML_SEQUENCES[i][0].test(lineText)) {
+      break;
+    }
+  }
+  if (i === HTML_SEQUENCES.length) {
+    return false;
+  }
+
+  if (silent) {
+    // true if this sequence can be a terminator, false otherwise
+    return HTML_SEQUENCES[i][2];
+  }
+
+  let nextLine = startLine + 1;
+
+  // If we are here - we detected HTML block.
+  // Let's roll down till block end.
+  if (!HTML_SEQUENCES[i][1].test(lineText)) {
+    for (; nextLine < endLine; nextLine++) {
+      if (state.sCount[nextLine] < state.blkIndent) {
+        break;
+      }
+
+      pos = state.bMarks[nextLine] + state.tShift[nextLine];
+      max = state.eMarks[nextLine];
+      lineText = state.src.slice(pos, max);
+
+      if (HTML_SEQUENCES[i][1].test(lineText)) {
+        if (lineText.length !== 0) {
+          nextLine++;
+        }
+        break;
+      }
+    }
+  }
+
+  state.line = nextLine;
+
+  const token = state.push("html_block", "", 0);
+  token.map = [startLine, nextLine];
+  token.content = state.getLines(startLine, nextLine, state.blkIndent, true);
+
+  return true;
+}
+
+export function setup(helper) {
+  helper.registerPlugin((md) => {
+    if (md.options.discourse.features["chat-html-block"]) {
+      md.block.ruler.push("chat-html-block", chatHtmlBlock);
+    }
+  });
+}

plugins/chat/assets/javascripts/lib/discourse-markdown/chat-html-inline.js

@@ -0,0 +1,106 @@
+// inspired from https://github.com/markdown-it/markdown-it/blob/master/lib/rules_inline/html_inline.mjs
+// note that allow lister will run on top of it, so if a tag is allowed here but not on
+// the allow list, then it won't show up
+
+const inline_names = ["kbd"];
+
+const patterns = inline_names.join("|");
+const attr_name = "[a-zA-Z_:][a-zA-Z0-9:._-]*";
+const unquoted = "[^\"'=<>`\\x00-\\x20]+";
+const single_quoted = "'[^']*'";
+const double_quoted = '"[^"]*"';
+const attr_value =
+  "(?:" + unquoted + "|" + single_quoted + "|" + double_quoted + ")";
+const attribute = "(?:\\s+" + attr_name + "(?:\\s*=\\s*" + attr_value + ")?)";
+const open_tag = `<(${patterns})` + attribute + "*\\s*\\/?>";
+const close_tag = `<\\/(${patterns})\\s*>`;
+const comment = "<!---?>|<!--(?:[^-]|-[^-]|--[^>])*-->";
+const processing = "<[?][\\s\\S]*?[?]>";
+const declaration = "<![A-Za-z][^>]*>";
+const cdata = "<!\\[CDATA\\[[\\s\\S]*?\\]\\]>";
+const HTML_TAG_RE = new RegExp(
+  "^(?:" +
+    open_tag +
+    "|" +
+    close_tag +
+    "|" +
+    comment +
+    "|" +
+    processing +
+    "|" +
+    declaration +
+    "|" +
+    cdata +
+    ")"
+);
+
+function isLinkOpen(str) {
+  return /^<a[>\s]/i.test(str);
+}
+function isLinkClose(str) {
+  return /^<\/a\s*>/i.test(str);
+}
+
+function isLetter(ch) {
+  /*eslint no-bitwise:0*/
+  let lc = ch | 0x20; // to lower case
+  return lc >= 0x61 /* a */ && lc <= 0x7a /* z */;
+}
+
+function chatHtmlInlineRule(state, silent) {
+  let ch,
+    match,
+    max,
+    token,
+    pos = state.pos;
+
+  if (!state.md.options.html) {
+    return false;
+  }
+
+  // Check start
+  max = state.posMax;
+  if (state.src.charCodeAt(pos) !== 0x3c /* < */ || pos + 2 >= max) {
+    return false;
+  }
+
+  // Quick fail on second char
+  ch = state.src.charCodeAt(pos + 1);
+  if (
+    ch !== 0x21 /* ! */ &&
+    ch !== 0x3f /* ? */ &&
+    ch !== 0x2f /* / */ &&
+    !isLetter(ch)
+  ) {
+    return false;
+  }
+
+  match = state.src.slice(pos).match(HTML_TAG_RE);
+
+  if (!match) {
+    return false;
+  }
+
+  if (!silent) {
+    token = state.push("html_inline", "", 0);
+
+    token.content = match[0];
+
+    if (isLinkOpen(token.content)) {
+      state.linkLevel++;
+    }
+    if (isLinkClose(token.content)) {
+      state.linkLevel--;
+    }
+  }
+  state.pos += match[0].length;
+  return true;
+}
+
+export function setup(helper) {
+  helper.registerPlugin((md) => {
+    if (md.options.discourse.features["chat-html-inline"]) {
+      md.inline.ruler.push("chat-html-inline", chatHtmlInlineRule);
+    }
+  });
+}