feat: Add support for config in frontmatter

cypress/integration/rendering/conf-and-directives.spec.js

@@ -14,7 +14,6 @@ describe('Configuration and directives - nodes should be light blue', () => {
         `,
       {}
     );
-    cy.get('svg');
   });
   it('Settings from initialize - nodes should be green', () => {
     imgSnapshotTest(
@@ -28,7 +27,6 @@ graph TD
           end          `,
       { theme: 'forest' }
     );
-    cy.get('svg');
   });
   it('Settings from initialize overriding themeVariable - nodes should be red', () => {
     imgSnapshotTest(
@@ -46,7 +44,6 @@ graph TD
         `,
       { theme: 'base', themeVariables: { primaryColor: '#ff0000' }, logLevel: 0 }
     );
-    cy.get('svg');
   });
   it('Settings from directive - nodes should be grey', () => {
     imgSnapshotTest(
@@ -62,7 +59,24 @@ graph TD
         `,
       {}
     );
-    cy.get('svg');
+  });
+  it('Settings from frontmatter - nodes should be grey', () => {
+    imgSnapshotTest(
+      `
+---
+config:
+  theme: neutral
+---
+graph TD
+          A(Start) --> B[/Another/]
+          A[/Another/] --> C[End]
+          subgraph section
+            B
+            C
+          end
+        `,
+      {}
+    );
   });
 
   it('Settings from directive overriding theme variable - nodes should be red', () => {
@@ -79,7 +93,6 @@ graph TD
         `,
       {}
     );
-    cy.get('svg');
   });
   it('Settings from initialize and directive - nodes should be grey', () => {
     imgSnapshotTest(
@@ -95,7 +108,6 @@ graph TD
         `,
       { theme: 'forest' }
     );
-    cy.get('svg');
   });
   it('Theme from initialize, directive overriding theme variable - nodes should be red', () => {
     imgSnapshotTest(
@@ -111,8 +123,50 @@ graph TD
         `,
       { theme: 'base' }
     );
-    cy.get('svg');
   });
+  it('Theme from initialize, frontmatter overriding theme variable - nodes should be red', () => {
+    imgSnapshotTest(
+      `
+---
+config:
+  theme: base
+  themeVariables:
+    primaryColor: '#ff0000'
+---
+graph TD
+          A(Start) --> B[/Another/]
+          A[/Another/] --> C[End]
+          subgraph section
+            B
+            C
+          end
+        `,
+      { theme: 'forest' }
+    );
+  });
+
+  it('should render if values are not quoted properly', () => {
+    // #ff0000 is not quoted properly, and will evaluate to null.
+    // This test ensures that the rendering still works.
+    imgSnapshotTest(
+      `---
+config:
+  theme: base
+  themeVariables:
+    primaryColor: #ff0000
+---
+graph TD
+          A(Start) --> B[/Another/]
+          A[/Another/] --> C[End]
+          subgraph section
+            B
+            C
+          end
+        `,
+      { theme: 'forest' }
+    );
+  });
+
   it('Theme variable from initialize, theme from directive - nodes should be red', () => {
     imgSnapshotTest(
       `
@@ -127,13 +181,11 @@ graph TD
         `,
       { themeVariables: { primaryColor: '#ff0000' } }
     );
-    cy.get('svg');
   });
   describe('when rendering several diagrams', () => {
     it('diagrams should not taint later diagrams', () => {
       const url = 'http://localhost:9000/theme-directives.html';
       cy.visit(url);
-      cy.get('svg');
       cy.matchImageSnapshot('conf-and-directives.spec-when-rendering-several-diagrams-diagram-1');
     });
   });

packages/mermaid/src/Diagram.ts

@@ -48,7 +48,7 @@ export class Diagram {
     // extractFrontMatter().
 
     this.parser.parse = (text: string) =>
-      originalParse(cleanupComments(extractFrontMatter(text, this.db)));
+      originalParse(cleanupComments(extractFrontMatter(text, this.db, configApi.addDirective)));
 
     this.parser.parser.yy = this.db;
     this.init = diagram.init;

packages/mermaid/src/config.ts

@@ -144,9 +144,12 @@ export const getConfig = (): MermaidConfig => {
  * @param options - The potential setConfig parameter
  */
 export const sanitize = (options: any) => {
+  if (!options) {
+    return;
+  }
   // Checking that options are not in the list of excluded options
   ['secure', ...(siteConfig.secure ?? [])].forEach((key) => {
-    if (options[key] !== undefined) {
+    if (Object.hasOwn(options, key)) {
       // DO NOT attempt to print options[key] within `${}` as a malicious script
       // can exploit the logger's attempt to stringify the value and execute arbitrary code
       log.debug(`Denied attempt to modify a secure key ${key}`, options[key]);
@@ -156,7 +159,7 @@ export const sanitize = (options: any) => {
 
   // Check that there no attempts of prototype pollution
   Object.keys(options).forEach((key) => {
-    if (key.indexOf('__') === 0) {
+    if (key.startsWith('__')) {
       delete options[key];
     }
   });

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

@@ -2,8 +2,13 @@ import { vi } from 'vitest';
 import { extractFrontMatter } from './frontmatter.js';
 
 const dbMock = () => ({ setDiagramTitle: vi.fn() });
+const setConfigMock = vi.fn();
 
 describe('extractFrontmatter', () => {
+  beforeEach(() => {
+    setConfigMock.mockClear();
+  });
+
   it('returns text unchanged if no frontmatter', () => {
     expect(extractFrontMatter('diagram', dbMock())).toEqual('diagram');
   });
@@ -75,4 +80,21 @@ describe('extractFrontmatter', () => {
       'tag suffix cannot contain exclamation marks'
     );
   });
+
+  it('handles frontmatter with config', () => {
+    const text = `---
+title: hello
+config:
+  graph:
+    string: hello
+    number: 14
+    boolean: false
+    array: [1, 2, 3]
+---
+diagram`;
+    expect(extractFrontMatter(text, {}, setConfigMock)).toEqual('diagram');
+    expect(setConfigMock).toHaveBeenCalledWith({
+      graph: { string: 'hello', number: 14, boolean: false, array: [1, 2, 3] },
+    });
+  });
 });

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

@@ -1,3 +1,4 @@
+import { MermaidConfig } from '../config.type.js';
 import { DiagramDB } from './types.js';
 // The "* as yaml" part is necessary for tree-shaking
 import * as yaml from 'js-yaml';
@@ -9,38 +10,50 @@ import * as yaml from 'js-yaml';
 // Relevant YAML spec: https://yaml.org/spec/1.2.2/#914-explicit-documents
 export const frontMatterRegex = /^-{3}\s*[\n\r](.*?)[\n\r]-{3}\s*[\n\r]+/s;
 
-type FrontMatterMetadata = {
+interface FrontMatterMetadata {
   title?: string;
   // Allows custom display modes. Currently used for compact mode in gantt charts.
   displayMode?: string;
-};
+  config?: MermaidConfig;
+}
 
 /**
  * Extract and parse frontmatter from text, if present, and sets appropriate
  * properties in the provided db.
  * @param text - The text that may have a YAML frontmatter.
  * @param db - Diagram database, could be of any diagram.
+ * @param setDiagramConfig - Optional function to set diagram config.
  * @returns text with frontmatter stripped out
  */
-export function extractFrontMatter(text: string, db: DiagramDB): string {
+export function extractFrontMatter(
+  text: string,
+  db: DiagramDB,
+  setDiagramConfig?: (config: MermaidConfig) => void
+): string {
   const matches = text.match(frontMatterRegex);
-  if (matches) {
-    const parsed: FrontMatterMetadata = yaml.load(matches[1], {
-      // To keep things simple, only allow strings, arrays, and plain objects.
-      // https://www.yaml.org/spec/1.2/spec.html#id2802346
-      schema: yaml.FAILSAFE_SCHEMA,
-    }) as FrontMatterMetadata;
-
-    if (parsed?.title) {
-      db.setDiagramTitle?.(parsed.title);
-    }
-
-    if (parsed?.displayMode) {
-      db.setDisplayMode?.(parsed.displayMode);
-    }
-
-    return text.slice(matches[0].length);
-  } else {
+  if (!matches) {
     return text;
   }
+
+  const parsed: FrontMatterMetadata = yaml.load(matches[1], {
+    // To support config, we need JSON schema.
+    // https://www.yaml.org/spec/1.2/spec.html#id2803231
+    schema: yaml.JSON_SCHEMA,
+  }) as FrontMatterMetadata;
+
+  if (parsed?.title) {
+    // toString() is necessary because YAML could parse the title as a number/boolean
+    db.setDiagramTitle?.(parsed.title.toString());
+  }
+
+  if (parsed?.displayMode) {
+    // toString() is necessary because YAML could parse the title as a number/boolean
+    db.setDisplayMode?.(parsed.displayMode.toString());
+  }
+
+  if (parsed?.config) {
+    setDiagramConfig?.(parsed.config);
+  }
+
+  return text.slice(matches[0].length);
 }

packages/mermaid/src/mermaidAPI.ts

@@ -30,6 +30,7 @@ import { evaluate } from './diagrams/common/common.js';
 import isEmpty from 'lodash-es/isEmpty.js';
 import { setA11yDiagramInfo, addSVGa11yTitleDescription } from './accessibility.js';
 import { parseDirective } from './directiveUtils.js';
+import { extractFrontMatter } from './diagram-api/frontmatter.js';
 
 // diagram names that support classDef statements
 const CLASSDEF_DIAGRAMS = [
@@ -385,7 +386,12 @@ const render = async function (
 
   configApi.reset();
 
-  // Add Directives. Must do this before getting the config and before creating the diagram.
+  // We need to add the directives before creating the diagram.
+  // So extractFrontMatter is called twice. Once here and once in the diagram parser.
+  // This can be fixed in a future refactor.
+  extractFrontMatter(text, {}, configApi.addDirective);
+
+  // Add Directives.
   const graphInit = utils.detectInit(text);
   if (graphInit) {
     configApi.addDirective(graphInit);

packages/mermaid/src/utils.ts

@@ -96,7 +96,10 @@ const directiveWithoutOpen =
  * @param config - Optional mermaid configuration object.
  * @returns The json object representing the init passed to mermaid.initialize()
  */
-export const detectInit = function (text: string, config?: MermaidConfig): MermaidConfig {
+export const detectInit = function (
+  text: string,
+  config?: MermaidConfig
+): MermaidConfig | undefined {
   const inits = detectDirective(text, /(?:init\b)|(?:initialize\b)/);
   let results = {};
 
@@ -106,20 +109,22 @@ export const detectInit = function (text: string, config?: MermaidConfig): Merma
   } else {
     results = inits.args;
   }
-  if (results) {
-    let type = detectType(text, config);
-    ['config'].forEach((prop) => {
-      if (results[prop] !== undefined) {
-        if (type === 'flowchart-v2') {
-          type = 'flowchart';
-        }
-        results[type] = results[prop];
-        delete results[prop];
-      }
-    });
+
+  if (!results) {
+    return;
   }
 
-  // Todo: refactor this, these results are never used
+  let type = detectType(text, config);
+  ['config'].forEach((prop) => {
+    if (results[prop] !== undefined) {
+      if (type === 'flowchart-v2') {
+        type = 'flowchart';
+      }
+      results[type] = results[prop];
+      delete results[prop];
+    }
+  });
+
   return results;
 };
 
@@ -844,7 +849,7 @@ export const sanitizeDirective = (args: unknown): void => {
   log.debug('sanitizeDirective called with', args);
 
   // Return if not an object
-  if (typeof args !== 'object') {
+  if (typeof args !== 'object' || args == null) {
     return;
   }
 
@@ -861,7 +866,8 @@ export const sanitizeDirective = (args: unknown): void => {
       key.startsWith('__') ||
       key.includes('proto') ||
       key.includes('constr') ||
-      !configKeys.has(key)
+      !configKeys.has(key) ||
+      args[key] == null
     ) {
       log.debug('sanitize deleting key: ', key);
       delete args[key];