fix: message parser being slow to process very long messages with too…

… many symbols (#33227)

.changeset/short-drinks-itch.md

@@ -0,0 +1,6 @@
+---
+'@rocket.chat/message-parser': patch
+'@rocket.chat/peggy-loader': patch
+---
+
+Improved the performance of the message parser

packages/message-parser/src/grammar.pegjs

@@ -10,6 +10,7 @@
  emoji,
  emojiUnicode,
  emoticon,
+ extractFirstResult,
  heading,
  image,
  inlineCode,
@@ -33,6 +34,11 @@
  unorderedList,
  timestamp,
  } = require('./utils');
+
+let skipBold = false;
+let skipItalic = false;
+let skipStrikethrough = false;
+let skipReferences = false;
 }}
 
 Start
@@ -212,7 +218,7 @@ Inline = value:(InlineItem / Any)+ EndOfLine? { return reducePlainTexts(value);
 
 InlineItem = Whitespace
  / Timestamp
- / References
+ / MaybeReferences
  / AutolinkedPhone
  / AutolinkedEmail
  / AutolinkedURL
@@ -240,7 +246,7 @@ References
  = "[" title:LinkTitle* "](" href:LinkRef ")" { return title.length ? link(href, reducePlainTexts(title)) : link(href); }
  / "<" href:LinkRef "|" title:LinkTitle2 ">" { return link(href, [plain(title)]); }
 
-LinkTitle = (Whitespace / EmphasisForReferences) / anyTitle:$(!("](" .) .) { return plain(anyTitle) }
+LinkTitle = (Whitespace / Emphasis) / anyTitle:$(!("](" .) .) { return plain(anyTitle) }
 
 LinkTitle2 = $([\x20-\x3B\x3D\x3F-\x60\x61-\x7B\x7D-\xFF] / NonASCII)+
 
@@ -349,14 +355,7 @@ AutoLinkURLBody = !(Extra* (Whitespace / EndOfLine)) .
  * Emphasis
  *
 */
-Emphasis = Bold / Italic / Strikethrough
-
-/**
- *
- * Emphasis for References
- *
-*/
-EmphasisForReferences = BoldForReferences / ItalicForReferences / StrikethroughForReferences
+Emphasis = MaybeBold / MaybeItalic / MaybeStrikethrough
 
 /**
  *
@@ -365,6 +364,63 @@ EmphasisForReferences = BoldForReferences / ItalicForReferences / StrikethroughF
  *
  */
 
+// This rule is used inside expressions that have a JS code ensuring they always fail,
+// Without any pattern to match, peggy will think the rule may end up succedding without consuming any input, which could cause infinite loops
+// So this unreachable rule is added to them to satisfy peggy's requirement.
+BlockedByJavascript = 'unreachable'
+
+MaybeBold
+ = result:(
+ & {
+ if (skipBold) { return false; }
+ skipBold = true;
+ return true;
+ }
+ (
+ (text:Bold { skipBold = false; return text; })
+ / (& { skipBold = false; return false; } BlockedByJavascript)
+ )
+ ) { return extractFirstResult(result); }
+
+MaybeStrikethrough
+ = result:(
+ & {
+ if (skipStrikethrough) { return false; }
+ skipStrikethrough = true;
+ return true;
+ }
+ (
+ (text:Strikethrough { skipStrikethrough = false; return text; })
+ / (& { skipStrikethrough = false; return false; } BlockedByJavascript)
+ )
+ ) { return extractFirstResult(result); }
+
+MaybeItalic
+ = result:(
+ & {
+ if (skipItalic) { return false; }
+ skipItalic = true;
+ return true;
+ }
+ (
+ (text:Italic { skipItalic = false; return text; })
+ / (& { skipItalic = false; return false; } BlockedByJavascript)
+ )
+ ) { return extractFirstResult(result); }
+
+MaybeReferences
+ = result:(
+ & {
+ if (skipReferences) { return false; }
+ skipReferences = true;
+ return true;
+ }
+ (
+ (text:References { skipReferences = false; return text; })
+ / (& { skipReferences = false; return false; } BlockedByJavascript)
+ )
+ ) { return extractFirstResult(result); }
+
 /* Italic */
 Italic
  = value:$([a-zA-Z0-9]+ [\x5F] [\x5F]?) { return plain(value); }
@@ -384,11 +440,11 @@ ItalicContentItems = text:ItalicContentItem+ { return reducePlainTexts(text); }
 ItalicContentItem
  = Whitespace
  / InlineCode
- / References
+ / MaybeReferences
  / UserMention
  / ChannelMention
- / Bold
- / Strikethrough
+ / MaybeBold
+ / MaybeStrikethrough
  / Emoji
  / Emoticon
  / AnyItalic
@@ -399,52 +455,12 @@ Bold = [\x2A] [\x2A] @BoldContent [\x2A] [\x2A] / [\x2A] @BoldContent [\x2A]
 
 BoldContent = text:BoldContentItem+ { return bold(reducePlainTexts(text)); }
 
-BoldContentItem = Whitespace / InlineCode / References / UserMention / ChannelMention / Italic / Strikethrough / Emoji / Emoticon / AnyBold / Line
+BoldContentItem = Whitespace / InlineCode / MaybeReferences / UserMention / ChannelMention / MaybeItalic / MaybeStrikethrough / Emoji / Emoticon / AnyBold / Line
 
 /* Strike */
 Strikethrough = [\x7E] [\x7E] @StrikethroughContent [\x7E] [\x7E] / [\x7E] @StrikethroughContent [\x7E]
 
-StrikethroughContent = text:(Timestamp / InlineCode / Whitespace / References / UserMention / ChannelMention / Italic / Bold / Emoji / Emoticon / AnyStrike / Line)+ {
- return strike(reducePlainTexts(text));
- }
-
-/* Italic for References */
-ItalicForReferences
- = value:$([a-zA-Z0-9]+ [\x5F] [\x5F]?) { return plain(value); }
- / [\x5F] [\x5F] i:ItalicContentItemsForReferences [\x5F] [\x5F] t:$[a-zA-Z0-9]+ {
- return reducePlainTexts([plain('__'), ...i, plain('__'), plain(t)])[0];
- }
- / [\x5F] i:ItalicContentItemsForReferences [\x5F] t:$[a-zA-Z]+ {
- return reducePlainTexts([plain('_'), ...i, plain('_'), plain(t)])[0];
- }
- / [\x5F] [\x5F] @ItalicContentForReferences [\x5F] [\x5F]
- / [\x5F] @ItalicContentForReferences [\x5F]
-
-ItalicContentForReferences = text:ItalicContentItemsForReferences { return italic(text); }
-
-ItalicContentItemsForReferences = text:ItalicContentItemForReferences+ { return reducePlainTexts(text); }
-
-ItalicContentItemForReferences
- = Whitespace
- / UserMention
- / ChannelMention
- / BoldForReferences
- / StrikethroughForReferences
- / Emoji
- / Emoticon
- / AnyItalic
- / Line
- / InlineCode
-
-/* Bold for References */
-BoldForReferences = [\x2A] [\x2A] @BoldContentForReferences [\x2A] [\x2A] / [\x2A] @BoldContentForReferences [\x2A]
-
-BoldContentForReferences = text:(Whitespace / UserMention / ChannelMention / ItalicForReferences / StrikethroughForReferences / Emoji / Emoticon / AnyBold / Line / InlineCode)+ { return bold(reducePlainTexts(text)); }
-
-/* Strike for References */
-StrikethroughForReferences = [\x7E] [\x7E] @StrikethroughContentForReferences [\x7E] [\x7E] / [\x7E] @StrikethroughContentForReferences [\x7E]
-
-StrikethroughContentForReferences = text:(Whitespace / UserMention / ChannelMention / ItalicForReferences / BoldForReferences / Emoji / Emoticon / AnyStrike / Line / InlineCode)+ {
+StrikethroughContent = text:(Timestamp / Whitespace / InlineCode / MaybeReferences / UserMention / ChannelMention / MaybeItalic / MaybeBold / Emoji / Emoticon / AnyStrike / Line)+ {
  return strike(reducePlainTexts(text));
  }
 

packages/message-parser/src/utils.ts

@@ -198,21 +198,19 @@ const joinEmoji = (
 export const reducePlainTexts = (
  values: Paragraph['value']
 ): Paragraph['value'] =>
- values
- .flatMap((item) => item)
- .reduce((result, item, index, values) => {
- const next = values[index + 1];
- const current = joinEmoji(item, values[index - 1], next);
- const previous: Inlines = result[result.length - 1];
-
- if (previous) {
- if (current.type === 'PLAIN_TEXT' && current.type === previous.type) {
- previous.value += current.value;
- return result;
- }
+ values.flat().reduce((result, item, index, values) => {
+ const next = values[index + 1];
+ const current = joinEmoji(item, values[index - 1], next);
+ const previous: Inlines = result[result.length - 1];
+
+ if (previous) {
+ if (current.type === 'PLAIN_TEXT' && current.type === previous.type) {
+ previous.value += current.value;
+ return result;
  }
- return [...result, current];
- }, [] as Paragraph['value']);
+ }
+ return [...result, current];
+ }, [] as Paragraph['value']);
 export const lineBreak = (): LineBreak => ({
  type: 'LINE_BREAK',
  value: undefined,
@@ -249,3 +247,13 @@ export const timestamp = (
  fallback: plain(`<t:${value}:${type || 't'}>`),
  };
 };
+
+export const extractFirstResult = (
+ value: Types[keyof Types]['value']
+): Types[keyof Types]['value'] => {
+ if (typeof value !== 'object' || !Array.isArray(value)) {
+ return value;
+ }
+
+ return value.filter((item) => item).shift() as Types[keyof Types]['value'];
+};