Merge pull request #4727 from Yokozuna59/add-info-langium-parser

feat: add `@mermaid-js/parser` package and `info` langium parser

.build/common.ts

@@ -2,6 +2,11 @@
  * Shared common options for both ESBuild and Vite
  */
 export const packageOptions = {
+  parser: {
+    name: 'mermaid-parser',
+    packageName: 'parser',
+    file: 'index.ts',
+  },
   mermaid: {
     name: 'mermaid',
     packageName: 'mermaid',

.build/generateLangium.ts

@@ -0,0 +1,5 @@
+import { generate } from 'langium-cli';
+
+export async function generateLangium() {
+  await generate({ file: `./packages/parser/langium-config.json` });
+}

.build/langium-cli.d.ts

@@ -0,0 +1,9 @@
+declare module 'langium-cli' {
+  export interface GenerateOptions {
+    file?: string;
+    mode?: 'development' | 'production';
+    watch?: boolean;
+  }
+
+  export function generate(options: GenerateOptions): Promise<boolean>;
+}

.esbuild/build.ts

@@ -2,6 +2,7 @@ import { build } from 'esbuild';
 import { mkdir, writeFile } from 'node:fs/promises';
 import { MermaidBuildOptions, defaultOptions, getBuildConfig } from './util.js';
 import { packageOptions } from '../.build/common.js';
+import { generateLangium } from '../.build/generateLangium.js';
 
 const shouldVisualize = process.argv.includes('--visualize');
 
@@ -52,9 +53,13 @@ const handler = (e) => {
 };
 
 const main = async () => {
+  await generateLangium();
   await mkdir('stats').catch(() => {});
   const packageNames = Object.keys(packageOptions) as (keyof typeof packageOptions)[];
-  await Promise.allSettled(packageNames.map((pkg) => buildPackage(pkg).catch(handler)));
+  // it should build `parser` before `mermaid` because it's a dependecy
+  for (const pkg of packageNames) {
+    await buildPackage(pkg).catch(handler);
+  }
 };
 
 void main();

.esbuild/server.ts

@@ -4,7 +4,11 @@ import cors from 'cors';
 import { getBuildConfig, defaultOptions } from './util.js';
 import { context } from 'esbuild';
 import chokidar from 'chokidar';
+import { generateLangium } from '../.build/generateLangium.js';
 
+const parserCtx = await context(
+  getBuildConfig({ ...defaultOptions, minify: false, core: false, entryName: 'parser' })
+);
 const mermaidCtx = await context(
   getBuildConfig({ ...defaultOptions, minify: false, core: false, entryName: 'mermaid' })
 );
@@ -28,7 +32,7 @@ const externalCtx = await context(
 const zenumlCtx = await context(
   getBuildConfig({ ...defaultOptions, minify: false, core: false, entryName: 'mermaid-zenuml' })
 );
-const contexts = [mermaidCtx, mermaidIIFECtx, externalCtx, zenumlCtx];
+const contexts = [parserCtx, mermaidCtx, mermaidIIFECtx, externalCtx, zenumlCtx];
 
 const rebuildAll = async () => {
   console.time('Rebuild time');
@@ -75,10 +79,11 @@ function sendEventsToAll() {
 }
 
 async function createServer() {
+  await generateLangium();
   handleFileChange();
   const app = express();
   chokidar
-    .watch('**/src/**/*.{js,ts,yaml,json}', {
+    .watch('**/src/**/*.{js,ts,langium,yaml,json}', {
       ignoreInitial: true,
       ignored: [/node_modules/, /dist/, /docs/, /coverage/],
     })
@@ -87,12 +92,16 @@ async function createServer() {
       if (!['add', 'change'].includes(event)) {
         return;
       }
+      if (/\.langium$/.test(path)) {
+        await generateLangium();
+      }
       console.log(`${path} changed. Rebuilding...`);
       handleFileChange();
     });
 
   app.use(cors());
   app.get('/events', eventsHandler);
+  app.use(express.static('./packages/parser/dist'));
   app.use(express.static('./packages/mermaid/dist'));
   app.use(express.static('./packages/mermaid-zenuml/dist'));
   app.use(express.static('./packages/mermaid-example-diagram/dist'));

.eslintignore

@@ -6,3 +6,6 @@ cypress/plugins/index.js
 coverage
 *.json
 node_modules
+
+# autogenereated by langium-cli
+generated/

.gitignore

@@ -47,3 +47,6 @@ stats/
 demos/dev/**
 !/demos/dev/example.html
 !/demos/dev/reload.js
+
+# autogenereated by langium-cli
+generated/

.prettierignore

@@ -10,3 +10,6 @@ stats
 .nyc_output
 # Autogenerated by `pnpm run --filter mermaid types:build-config`
 packages/mermaid/src/config.type.ts
+
+# autogenereated by langium-cli
+generated/

.vite/build.ts

@@ -8,6 +8,7 @@ import { visualizer } from 'rollup-plugin-visualizer';
 import type { TemplateType } from 'rollup-plugin-visualizer/dist/plugin/template-types.js';
 import istanbul from 'vite-plugin-istanbul';
 import { packageOptions } from '../.build/common.js';
+import { generateLangium } from '../.build/generateLangium.js';
 
 const visualize = process.argv.includes('--visualize');
 const watch = process.argv.includes('--watch');
@@ -82,7 +83,7 @@ export const getBuildConfig = ({ minify, core, watch, entryName }: BuildOptions)
       // @ts-expect-error According to the type definitions, rollup plugins are incompatible with vite
       typescript({ compilerOptions: { declaration: false } }),
       istanbul({
-        exclude: ['node_modules', 'test/', '__mocks__'],
+        exclude: ['node_modules', 'test/', '__mocks__', 'generated'],
         extension: ['.js', '.ts'],
         requireEnv: true,
         forceBuildInstrument: coverage,
@@ -106,18 +107,24 @@ const buildPackage = async (entryName: keyof typeof packageOptions) => {
 
 const main = async () => {
   const packageNames = Object.keys(packageOptions) as (keyof typeof packageOptions)[];
-  for (const pkg of packageNames.filter((pkg) => !mermaidOnly || pkg === 'mermaid')) {
+  for (const pkg of packageNames.filter(
+    (pkg) => !mermaidOnly || pkg === 'mermaid' || pkg === 'parser'
+  )) {
     await buildPackage(pkg);
   }
 };
 
+await generateLangium();
+
 if (watch) {
+  await build(getBuildConfig({ minify: false, watch, core: false, entryName: 'parser' }));
   build(getBuildConfig({ minify: false, watch, core: false, entryName: 'mermaid' }));
   if (!mermaidOnly) {
     build(getBuildConfig({ minify: false, watch, entryName: 'mermaid-example-diagram' }));
     build(getBuildConfig({ minify: false, watch, entryName: 'mermaid-zenuml' }));
   }
 } else if (visualize) {
+  await build(getBuildConfig({ minify: false, watch, core: false, entryName: 'parser' }));
   await build(getBuildConfig({ minify: false, core: true, entryName: 'mermaid' }));
   await build(getBuildConfig({ minify: false, core: false, entryName: 'mermaid' }));
 } else {

.vite/server.ts

@@ -14,6 +14,7 @@ async function createServer() {
   });
 
   app.use(cors());
+  app.use(express.static('./packages/parser/dist'));
   app.use(express.static('./packages/mermaid/dist'));
   app.use(express.static('./packages/mermaid-zenuml/dist'));
   app.use(express.static('./packages/mermaid-example-diagram/dist'));

cSpell.json

@@ -71,6 +71,7 @@
     "knut",
     "knutsveidqvist",
     "laganeckas",
+    "langium",
     "linetype",
     "lintstagedrc",
     "logmsg",

package.json

@@ -15,11 +15,11 @@
     "git graph"
   ],
   "scripts": {
-    "build": "pnpm run -r clean && pnpm build:esbuild && pnpm build:types",
+    "build": "pnpm build:esbuild && pnpm build:types",
     "build:esbuild": "pnpm run -r clean && ts-node-esm --transpileOnly .esbuild/build.ts",
     "build:mermaid": "pnpm build:esbuild --mermaid",
     "build:viz": "pnpm build:esbuild --visualize",
-    "build:types": "tsc -p ./packages/mermaid/tsconfig.json --emitDeclarationOnly && tsc -p ./packages/mermaid-zenuml/tsconfig.json --emitDeclarationOnly && tsc -p ./packages/mermaid-example-diagram/tsconfig.json --emitDeclarationOnly",
+    "build:types": "tsc -p ./packages/parser/tsconfig.json --emitDeclarationOnly && tsc -p ./packages/mermaid/tsconfig.json --emitDeclarationOnly && tsc -p ./packages/mermaid-zenuml/tsconfig.json --emitDeclarationOnly && tsc -p ./packages/mermaid-example-diagram/tsconfig.json --emitDeclarationOnly",
     "dev": "ts-node-esm --transpileOnly .esbuild/server.ts",
     "dev:vite": "ts-node-esm --transpileOnly .vite/server.ts",
     "dev:coverage": "pnpm coverage:cypress:clean && VITE_COVERAGE=true pnpm dev:vite",
@@ -107,6 +107,7 @@
     "jison": "^0.4.18",
     "js-yaml": "^4.1.0",
     "jsdom": "^22.0.0",
+    "langium-cli": "2.0.1",
     "lint-staged": "^13.2.1",
     "nyc": "^15.1.0",
     "path-browserify": "^1.0.1",

packages/mermaid-zenuml/src/parser.ts

@@ -5,7 +5,6 @@
  * This is a dummy parser that satisfies the mermaid API logic.
  */
 export default {
-  parser: { yy: {} },
   parse: () => {
     // no op
   },

packages/mermaid/package.json

@@ -72,6 +72,7 @@
     "khroma": "^2.0.0",
     "lodash-es": "^4.17.21",
     "mdast-util-from-markdown": "^1.3.0",
+    "mermaid-parser": "workspace:^",
     "stylis": "^4.1.3",
     "ts-dedent": "^2.2.0",
     "uuid": "^9.0.0"

packages/mermaid/src/Diagram.ts

@@ -50,7 +50,10 @@ export class Diagram {
     this.parser.parse = (text: string) =>
       originalParse(cleanupComments(extractFrontMatter(text, this.db, configApi.addDirective)));
 
-    this.parser.parser.yy = this.db;
+    if (this.parser.parser !== undefined) {
+      // The parser.parser.yy is only present in JISON parsers. So, we'll only set if required.
+      this.parser.parser.yy = this.db;
+    }
     this.init = diagram.init;
     this.parse();
   }

packages/mermaid/src/diagram-api/diagram-orchestration.ts

@@ -45,7 +45,6 @@ export const addDiagrams = () => {
       styles: {}, // should never be used
       renderer: {}, // should never be used
       parser: {
-        parser: { yy: {} },
         parse: () => {
           throw new Error(
             'Diagrams beginning with --- are not valid. ' +

packages/mermaid/src/diagram-api/diagramAPI.spec.ts

@@ -39,7 +39,6 @@ describe('DiagramAPI', () => {
           parse: (_text) => {
             return;
           },
-          parser: { yy: {} },
         },
         renderer: {},
         styles: {},

packages/mermaid/src/diagram-api/types.ts

@@ -80,7 +80,7 @@ export type DrawDefinition = (
 
 export interface ParserDefinition {
   parse: (text: string) => void;
-  parser: { yy: DiagramDB };
+  parser?: { yy: DiagramDB };
 }
 
 /**

packages/mermaid/src/diagram.spec.ts

@@ -30,9 +30,6 @@ describe('diagram detection', () => {
               parse: () => {
                 // no-op
               },
-              parser: {
-                yy: {},
-              },
             },
             renderer: {},
             styles: {},

packages/mermaid/src/diagrams/common/populateCommonDb.ts

@@ -0,0 +1,15 @@
+import type { DiagramAST } from 'mermaid-parser';
+
+import type { DiagramDB } from '../../diagram-api/types.js';
+
+export function populateCommonDb(ast: DiagramAST, db: DiagramDB) {
+  if (ast.accDescr) {
+    db.setAccDescription?.(ast.accDescr);
+  }
+  if (ast.accTitle) {
+    db.setAccTitle?.(ast.accTitle);
+  }
+  if (ast.title) {
+    db.setDiagramTitle?.(ast.title);
+  }
+}

packages/mermaid/src/diagrams/error/errorDiagram.ts

@@ -5,7 +5,6 @@ const diagram: DiagramDefinition = {
   db: {},
   renderer,
   parser: {
-    parser: { yy: {} },
     parse: (): void => {
       return;
     },

packages/mermaid/src/diagrams/info/info.spec.ts

@@ -1,24 +1,31 @@
-// @ts-ignore - jison doesn't export types
+import { parser } from './infoParser.js';
-import { parser } from './parser/info.jison';
-import { db } from './infoDb.js';
-
-describe('info diagram', () => {
-  beforeEach(() => {
-    parser.yy = db;
-    parser.yy.clear();
-  });
 
+describe('info', () => {
   it('should handle an info definition', () => {
     const str = `info`;
-    parser.parse(str);
+    expect(() => {
-
+      parser.parse(str);
-    expect(db.getInfo()).toBeFalsy();
+    }).not.toThrow();
   });
 
   it('should handle an info definition with showInfo', () => {
     const str = `info showInfo`;
-    parser.parse(str);
+    expect(() => {
+      parser.parse(str);
+    }).not.toThrow();
+  });
 
-    expect(db.getInfo()).toBeTruthy();
+  it('should throw because of unsupported info grammar', () => {
+    const str = `info unsupported`;
+    expect(() => {
+      parser.parse(str);
+    }).toThrow('Parsing failed: unexpected character: ->u<- at offset: 5, skipped 11 characters.');
+  });
+
+  it('should throw because of unsupported info grammar', () => {
+    const str = `info unsupported`;
+    expect(() => {
+      parser.parse(str);
+    }).toThrow('Parsing failed: unexpected character: ->u<- at offset: 5, skipped 11 characters.');
   });
 });

packages/mermaid/src/diagrams/info/infoDb.ts

@@ -1,23 +1,10 @@
 import type { InfoFields, InfoDB } from './infoTypes.js';
+import { version } from '../../../package.json';
 
-export const DEFAULT_INFO_DB: InfoFields = {
+export const DEFAULT_INFO_DB: InfoFields = { version } as const;
-  info: false,
-} as const;
 
-let info: boolean = DEFAULT_INFO_DB.info;
+export const getVersion = (): string => DEFAULT_INFO_DB.version;
-
-export const setInfo = (toggle: boolean): void => {
-  info = toggle;
-};
-
-export const getInfo = (): boolean => info;
-
-const clear = (): void => {
-  info = DEFAULT_INFO_DB.info;
-};
 
 export const db: InfoDB = {
-  clear,
+  getVersion,
-  setInfo,
-  getInfo,
 };

packages/mermaid/src/diagrams/info/infoDiagram.ts

@@ -1,6 +1,5 @@
 import type { DiagramDefinition } from '../../diagram-api/types.js';
-// @ts-ignore - jison doesn't export types
+import { parser } from './infoParser.js';
-import parser from './parser/info.jison';
 import { db } from './infoDb.js';
 import { renderer } from './infoRenderer.js';
 

packages/mermaid/src/diagrams/info/infoParser.ts

@@ -0,0 +1,12 @@
+import type { Info } from 'mermaid-parser';
+import { parse } from 'mermaid-parser';
+
+import { log } from '../../logger.js';
+import type { ParserDefinition } from '../../diagram-api/types.js';
+
+export const parser: ParserDefinition = {
+  parse: (input: string): void => {
+    const ast: Info = parse('info', input);
+    log.debug(ast);
+  },
+};

packages/mermaid/src/diagrams/info/infoTypes.ts

@@ -1,11 +1,9 @@
 import type { DiagramDB } from '../../diagram-api/types.js';
 
 export interface InfoFields {
-  info: boolean;
+  version: string;
 }
 
 export interface InfoDB extends DiagramDB {
-  clear: () => void;
+  getVersion: () => string;
-  setInfo: (info: boolean) => void;
-  getInfo: () => boolean;
 }

packages/mermaid/src/diagrams/info/parser/info.jison

@@ -1,48 +0,0 @@
-/** mermaid
- *  https://knsv.github.io/mermaid
- *  (c) 2015 Knut Sveidqvist
- *  MIT license.
- */
-%lex
-
-%options case-insensitive
-
-%{
-	// Pre-lexer code can go here
-%}
-
-%%
-
-"info"		      return 'info'    ;
-[\s\n\r]+         return 'NL'      ;
-[\s]+ 		      return 'space';
-"showInfo"		  return 'showInfo';
-<<EOF>>           return 'EOF'     ;
-.                 return 'TXT' ;
-
-/lex
-
-%start start
-
-%% /* language grammar */
-
-start
-// %{	: info document 'EOF' { return yy; } }
-	: info document 'EOF' { return yy; }
-	;
-
-document
-	: /* empty */
-	| document line
-	;
-
-line
-	: statement { }
-	| 'NL'
-	;
-
-statement
-	:  showInfo   { yy.setInfo(true);  }
-	;
-
-%%

packages/mermaid/src/mermaid.spec.ts

@@ -102,7 +102,6 @@ describe('when using mermaid and ', () => {
           parse: (_text) => {
             return;
           },
-          parser: { yy: {} },
         },
         styles: () => {
           // do nothing

packages/parser/LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2023 Yokozuna59
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/parser/README.md

@@ -0,0 +1,63 @@
+<p align="center">
+<img src="https://raw.githubusercontent.com/mermaid-js/mermaid/develop/docs/public/favicon.svg" height="150">
+
+</p>
+<h1 align="center">
+Mermaid Parser
+</h1>
+
+<p align="center">
+Mermaid parser package
+<p>
+
+[![NPM](https://img.shields.io/npm/v/mermaid-parser)](https://www.npmjs.com/package/mermaid-parser)
+
+## How the package works
+
+The package exports a `parse` function that has two parameters:
+
+```ts
+declare function parse<T extends DiagramAST>(
+  diagramType: keyof typeof initializers,
+  text: string
+): T;
+```
+
+## How does a Langium-based parser work?
+
+```mermaid
+sequenceDiagram
+actor Package
+participant Module
+participant TokenBuilder
+participant Lexer
+participant Parser
+participant ValueConverter
+
+
+Package ->> Module: Create services
+Module ->> TokenBuilder: Override or/and<br>reorder rules
+TokenBuilder ->> Lexer: Read the string and transform<br>it into a token stream
+Lexer ->> Parser: Parse token<br>stream into AST
+Parser ->> ValueConverter: Clean/modify tokenized<br>rules returned value
+ValueConverter -->> Package: Return AST
+```
+
+- When to override `TokenBuilder`?
+
+  - To override keyword rules.
+  - To override terminal rules that need a custom function.
+  - To manually reorder the list of rules.
+
+- When to override `Lexer`?
+
+  - To modify input before tokenizing.
+  - To insert/modify tokens that cannot or have not been parsed.
+
+- When to override `LangiumParser`?
+
+  - To insert or modify attributes that can't be parsed.
+
+- When to override `ValueConverter`?
+
+  - To modify the returned value from the parser.

packages/parser/langium-config.json

@@ -0,0 +1,13 @@
+{
+  "projectName": "Mermaid",
+  "languages": [
+    {
+      "id": "info",
+      "grammar": "src/language/info/info.langium",
+      "fileExtensions": [".mmd", ".mermaid"]
+    }
+  ],
+  "mode": "production",
+  "importExtension": ".js",
+  "out": "src/language/generated"
+}

packages/parser/package.json

@@ -0,0 +1,48 @@
+{
+  "name": "mermaid-parser",
+  "version": "0.2.0",
+  "description": "MermaidJS parser",
+  "author": "Yokozuna59",
+  "contributors": [
+    "Yokozuna59",
+    "Sidharth Vinod (https://sidharth.dev)"
+  ],
+  "homepage": "https://github.com/mermaid-js/mermaid/tree/develop/packages/mermaid/parser/#readme",
+  "types": "dist/src/index.d.ts",
+  "type": "module",
+  "exports": {
+    ".": {
+      "import": "./dist/mermaid-parser.esm.mjs",
+      "types": "./dist/src/index.d.ts"
+    }
+  },
+  "scripts": {
+    "clean": "rimraf dist src/language/generated",
+    "langium:generate": "langium generate",
+    "langium:watch": "langium generate --watch",
+    "prepublishOnly": "pnpm -w run build"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/mermaid-js/mermaid.git",
+    "directory": "packages/parser"
+  },
+  "license": "MIT",
+  "keywords": [
+    "mermaid",
+    "parser",
+    "ast"
+  ],
+  "dependencies": {
+    "langium": "2.0.1"
+  },
+  "devDependencies": {
+    "langium-cli": "2.0.1"
+  },
+  "files": [
+    "dist/"
+  ],
+  "publishConfig": {
+    "access": "public"
+  }
+}

packages/parser/src/index.ts

@@ -0,0 +1,3 @@
+export type { Info } from './language/index.js';
+export type { DiagramAST } from './parse.js';
+export { parse, MermaidParseError } from './parse.js';

packages/parser/src/language/chevrotainWrapper.ts

@@ -0,0 +1,51 @@
+/* eslint-disable @typescript-eslint/no-explicit-any */
+
+type CustomPatternMatcherReturn = [string] & { payload?: any };
+
+export type CustomPatternMatcherFunc = (
+  text: string,
+  offset: number,
+  tokens: IToken[],
+  groups: {
+    [groupName: string]: IToken[];
+  }
+) => CustomPatternMatcherReturn | RegExpExecArray | null;
+
+interface ICustomPattern {
+  exec: CustomPatternMatcherFunc;
+}
+
+type TokenPattern = RegExp | string | CustomPatternMatcherFunc | ICustomPattern;
+
+export interface IToken {
+  image: string;
+  startOffset: number;
+  startLine?: number;
+  startColumn?: number;
+  endOffset?: number;
+  endLine?: number;
+  endColumn?: number;
+  isInsertedInRecovery?: boolean;
+  tokenTypeIdx: number;
+  tokenType: TokenType;
+  payload?: any;
+}
+
+export interface TokenType {
+  name: string;
+  GROUP?: string;
+  PATTERN?: TokenPattern;
+  LABEL?: string;
+  LONGER_ALT?: TokenType | TokenType[];
+  POP_MODE?: boolean;
+  PUSH_MODE?: string;
+  LINE_BREAKS?: boolean;
+  CATEGORIES?: TokenType[];
+  tokenTypeIdx?: number;
+  categoryMatches?: number[];
+  categoryMatchesMap?: {
+    [tokType: number]: boolean;
+  };
+  isParent?: boolean;
+  START_CHARS_HINT?: (string | number)[];
+}

packages/parser/src/language/common/common.langium

@@ -0,0 +1,14 @@
+fragment TitleAndAccessibilities:
+  ((accDescr=ACC_DESCR | accTitle=ACC_TITLE | title=TITLE) NEWLINE+)+
+;
+
+terminal NEWLINE: /\r?\n/;
+terminal ACC_DESCR: /accDescr(?:[\t ]*:[\t ]*[^\n\r]*?(?=%%)|\s*{[^}]*})|accDescr(?:[\t ]*:[\t ]*[^\n\r]*|\s*{[^}]*})/;
+terminal ACC_TITLE: /accTitle[\t ]*:[\t ]*[^\n\r]*?(?=%%)|accTitle[\t ]*:[\t ]*[^\n\r]*/;
+terminal TITLE: /title(?:[\t ]+[^\n\r]*?|)(?=%%)|title(?:[\t ]+[^\n\r]*|)/;
+
+hidden terminal WHITESPACE: /[\t ]+/;
+// TODO: add YAML_COMMENT hidden rule without interfere actual grammar
+hidden terminal YAML: /---[\t ]*\r?\n[\S\s]*?---[\t ]*(?!.)/;
+hidden terminal DIRECTIVE: /[\t ]*%%{[\S\s]*?}%%\s*/;
+hidden terminal SINGLE_LINE_COMMENT: /[\t ]*%%[^\n\r]*/;

packages/parser/src/language/common/commonLexer.ts

@@ -0,0 +1,8 @@
+import type { LexerResult } from 'langium';
+import { DefaultLexer } from 'langium';
+
+export class CommonLexer extends DefaultLexer {
+  public override tokenize(text: string): LexerResult {
+    return super.tokenize(text + '\n');
+  }
+}

packages/parser/src/language/common/commonMatcher.ts

@@ -0,0 +1,14 @@
+/**
+ * Matches single and multiline accessible description
+ */
+export const accessibilityDescrRegex = /accDescr(?:[\t ]*:[\t ]*([^\n\r]*)|\s*{([^}]*)})/;
+
+/**
+ * Matches single line accessible title
+ */
+export const accessibilityTitleRegex = /accTitle[\t ]*:[\t ]*([^\n\r]*)/;
+
+/**
+ * Matches a single line title
+ */
+export const titleRegex = /title([\t ]+([^\n\r]*)|)/;

packages/parser/src/language/common/commonValueConverters.ts

@@ -0,0 +1,74 @@
+import type { CstNode, GrammarAST, ValueType } from 'langium';
+import { DefaultValueConverter } from 'langium';
+
+import { accessibilityDescrRegex, accessibilityTitleRegex, titleRegex } from './commonMatcher.js';
+
+export class CommonValueConverter extends DefaultValueConverter {
+  protected override runConverter(
+    rule: GrammarAST.AbstractRule,
+    input: string,
+    cstNode: CstNode
+  ): ValueType {
+    const value: ValueType | undefined = CommonValueConverter.customRunConverter(
+      rule,
+      input,
+      cstNode
+    );
+    if (value === undefined) {
+      return super.runConverter(rule, input, cstNode);
+    } else {
+      return value;
+    }
+  }
+
+  /**
+   * A method contains convert logic to be used by class itself or `MermaidValueConverter`.
+   *
+   * @param rule - Parsed rule.
+   * @param input - Matched string.
+   * @param _cstNode - Node in the Concrete Syntax Tree (CST).
+   * @returns converted the value if it's common rule or `undefined` if it's not.
+   */
+  public static customRunConverter(
+    rule: GrammarAST.AbstractRule,
+    input: string,
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    _cstNode: CstNode
+  ): ValueType | undefined {
+    let regex: RegExp | undefined;
+    switch (rule.name) {
+      case 'ACC_DESCR': {
+        regex = new RegExp(accessibilityDescrRegex.source);
+        break;
+      }
+      case 'ACC_TITLE': {
+        regex = new RegExp(accessibilityTitleRegex.source);
+        break;
+      }
+      case 'TITLE': {
+        regex = new RegExp(titleRegex.source);
+        break;
+      }
+    }
+    if (regex === undefined) {
+      return undefined;
+    }
+    const match = regex.exec(input);
+    if (match === null) {
+      return undefined;
+    }
+    // single line title, accTitle, accDescr
+    if (match[1] !== undefined) {
+      return match[1].trim().replaceAll(/[\t ]{2,}/gm, ' ');
+    }
+    // multi line accDescr
+    if (match[2] !== undefined) {
+      return match[2]
+        .replaceAll(/^\s*/gm, '')
+        .replaceAll(/\s+$/gm, '')
+        .replaceAll(/[\t ]{2,}/gm, ' ')
+        .replaceAll(/[\n\r]{2,}/gm, '\n');
+    }
+    return undefined;
+  }
+}

packages/parser/src/language/common/index.ts

@@ -0,0 +1,2 @@
+export * from './commonLexer.js';
+export * from './commonValueConverters.js';

packages/parser/src/language/index.ts

@@ -0,0 +1,6 @@
+export * from './generated/ast.js';
+export * from './generated/grammar.js';
+export * from './generated/module.js';
+
+export * from './common/index.js';
+export * from './info/index.js';

packages/parser/src/language/info/index.ts

@@ -0,0 +1 @@
+export * from './infoModule.js';

packages/parser/src/language/info/info.langium

@@ -0,0 +1,9 @@
+grammar Info
+import "../common/common";
+
+entry Info:
+  NEWLINE*
+  "info" NEWLINE*
+  ("showInfo" NEWLINE*)?
+  TitleAndAccessibilities?
+;

packages/parser/src/language/info/infoModule.ts

@@ -0,0 +1,72 @@
+import type {
+  DefaultSharedModuleContext,
+  LangiumServices,
+  LangiumSharedServices,
+  Module,
+  PartialLangiumServices,
+} from 'langium';
+import { EmptyFileSystem, createDefaultModule, createDefaultSharedModule, inject } from 'langium';
+
+import { MermaidGeneratedSharedModule, InfoGeneratedModule } from '../generated/module.js';
+import { CommonLexer } from '../common/commonLexer.js';
+import { CommonValueConverter } from '../common/commonValueConverters.js';
+import { InfoTokenBuilder } from './infoTokenBuilder.js';
+
+/**
+ * Declaration of `Info` services.
+ */
+type InfoAddedServices = {
+  parser: {
+    Lexer: CommonLexer;
+    TokenBuilder: InfoTokenBuilder;
+    ValueConverter: CommonValueConverter;
+  };
+};
+
+/**
+ * Union of Langium default services and `Info` services.
+ */
+export type InfoServices = LangiumServices & InfoAddedServices;
+
+/**
+ * Dependency injection module that overrides Langium default services and
+ * contributes the declared `Info` services.
+ */
+export const InfoModule: Module<InfoServices, PartialLangiumServices & InfoAddedServices> = {
+  parser: {
+    Lexer: (services) => new CommonLexer(services),
+    TokenBuilder: () => new InfoTokenBuilder(),
+    ValueConverter: () => new CommonValueConverter(),
+  },
+};
+
+/**
+ * Create the full set of services required by Langium.
+ *
+ * First inject the shared services by merging two modules:
+ *  - Langium default shared services
+ *  - Services generated by langium-cli
+ *
+ * Then inject the language-specific services by merging three modules:
+ *  - Langium default language-specific services
+ *  - Services generated by langium-cli
+ *  - Services specified in this file
+ * @param context - Optional module context with the LSP connection
+ * @returns An object wrapping the shared services and the language-specific services
+ */
+export function createInfoServices(context: DefaultSharedModuleContext = EmptyFileSystem): {
+  shared: LangiumSharedServices;
+  Info: InfoServices;
+} {
+  const shared: LangiumSharedServices = inject(
+    createDefaultSharedModule(context),
+    MermaidGeneratedSharedModule
+  );
+  const Info: InfoServices = inject(
+    createDefaultModule({ shared }),
+    InfoGeneratedModule,
+    InfoModule
+  );
+  shared.ServiceRegistry.register(Info);
+  return { shared, Info };
+}

packages/parser/src/language/info/infoTokenBuilder.ts

@@ -0,0 +1,24 @@
+import type { GrammarAST, Stream, TokenBuilderOptions } from 'langium';
+import { DefaultTokenBuilder } from 'langium';
+
+import type { TokenType } from '../chevrotainWrapper.js';
+
+export class InfoTokenBuilder extends DefaultTokenBuilder {
+  protected override buildKeywordTokens(
+    rules: Stream<GrammarAST.AbstractRule>,
+    terminalTokens: TokenType[],
+    options?: TokenBuilderOptions
+  ): TokenType[] {
+    const tokenTypes: TokenType[] = super.buildKeywordTokens(rules, terminalTokens, options);
+    // to restrict users, they mustn't have any non-whitespace characters after the keyword.
+    tokenTypes.forEach((tokenType: TokenType): void => {
+      if (
+        (tokenType.name === 'info' || tokenType.name === 'showInfo') &&
+        tokenType.PATTERN !== undefined
+      ) {
+        tokenType.PATTERN = new RegExp(tokenType.PATTERN.toString() + '(?!\\S)');
+      }
+    });
+    return tokenTypes;
+  }
+}

packages/parser/src/parse.ts

@@ -0,0 +1,43 @@
+import type { LangiumParser, ParseResult } from 'langium';
+import type { Info } from './index.js';
+import { createInfoServices } from './language/index.js';
+
+export type DiagramAST = Info;
+
+const parsers: Record<string, LangiumParser> = {};
+
+const initializers = {
+  info: () => {
+    // Will have to make parse async to use this. Can try later...
+    // const { createInfoServices } = await import('./language/info/index.js');
+    const parser = createInfoServices().Info.parser.LangiumParser;
+    parsers['info'] = parser;
+  },
+} as const;
+export function parse(diagramType: 'info', text: string): Info;
+export function parse<T extends DiagramAST>(
+  diagramType: keyof typeof initializers,
+  text: string
+): T {
+  const initializer = initializers[diagramType];
+  if (!initializer) {
+    throw new Error(`Unknown diagram type: ${diagramType}`);
+  }
+  if (!parsers[diagramType]) {
+    initializer();
+  }
+  const parser: LangiumParser = parsers[diagramType];
+  const result: ParseResult<T> = parser.parse<T>(text);
+  if (result.lexerErrors.length > 0 || result.parserErrors.length > 0) {
+    throw new MermaidParseError(result);
+  }
+  return result.value;
+}
+
+export class MermaidParseError extends Error {
+  constructor(public result: ParseResult<DiagramAST>) {
+    const lexerErrors: string = result.lexerErrors.map((err) => err.message).join('\n');
+    const parserErrors: string = result.parserErrors.map((err) => err.message).join('\n');
+    super(`Parsing failed: ${lexerErrors} ${parserErrors}`);
+  }
+}

packages/parser/tests/info.test.ts

@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest';
+import type { LangiumParser, ParseResult } from 'langium';
+
+import type { InfoServices } from '../src/language/index.js';
+import { Info, createInfoServices } from '../src/language/index.js';
+import { noErrorsOrAlternatives } from './test-util.js';
+
+const services: InfoServices = createInfoServices().Info;
+const parser: LangiumParser = services.parser.LangiumParser;
+function createInfoTestServices(): {
+  services: InfoServices;
+  parse: (input: string) => ParseResult<Info>;
+} {
+  const parse = (input: string) => {
+    return parser.parse<Info>(input);
+  };
+
+  return { services, parse };
+}
+
+describe('info', () => {
+  const { parse } = createInfoTestServices();
+
+  it.each([
+    `info`,
+    `
+    info`,
+    `info
+    `,
+    `
+    info
+    `,
+  ])('should handle empty info', (context: string) => {
+    const result = parse(context);
+    noErrorsOrAlternatives(result);
+
+    expect(result.value.$type).toBe(Info);
+  });
+
+  it.each([
+    `info showInfo`,
+    `
+    info showInfo`,
+    `info
+    showInfo
+    `,
+    `
+    info
+    showInfo
+    `,
+  ])('should handle showInfo', (context: string) => {
+    const result = parse(context);
+    noErrorsOrAlternatives(result);
+
+    expect(result.value.$type).toBe(Info);
+  });
+});

packages/parser/tests/test-util.ts

@@ -0,0 +1,18 @@
+import { expect, vi } from 'vitest';
+import type { ParseResult } from 'langium';
+
+const consoleMock = vi.spyOn(console, 'log').mockImplementation(() => undefined);
+
+/**
+ * A helper test function that validate that the result doesn't have errors
+ * or any ambiguous alternatives from chevrotain.
+ *
+ * @param result - the result `parse` function.
+ */
+export function noErrorsOrAlternatives(result: ParseResult) {
+  expect(result.lexerErrors).toHaveLength(0);
+  expect(result.parserErrors).toHaveLength(0);
+
+  expect(consoleMock).not.toHaveBeenCalled();
+  consoleMock.mockReset();
+}

packages/parser/tsconfig.json

@@ -0,0 +1,12 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": ".",
+    "outDir": "./dist",
+    "allowJs": false,
+    "preserveSymlinks": false,
+    "strictPropertyInitialization": false
+  },
+  "include": ["./src/**/*.ts", "./tests/**/*.ts"],
+  "typeRoots": ["./src/types"]
+}

vite.config.ts

@@ -1,7 +1,7 @@
 import jison from './.vite/jisonPlugin.js';
 import jsonSchemaPlugin from './.vite/jsonSchemaPlugin.js';
 import typescript from '@rollup/plugin-typescript';
-import { defineConfig } from 'vitest/config';
+import { defaultExclude, defineConfig } from 'vitest/config';
 
 export default defineConfig({
   resolve: {
@@ -22,7 +22,7 @@ export default defineConfig({
       provider: 'v8',
       reporter: ['text', 'json', 'html', 'lcov'],
       reportsDirectory: './coverage/vitest',
-      exclude: ['**/node_modules/**', '**/tests/**', '**/__mocks__/**'],
+      exclude: [...defaultExclude, './tests/**', '**/__mocks__/**', '**/generated/'],
     },
   },
   build: {