mermaid-js · sidharthv96 · Mar 23, 2024 · Apr 29, 2023 · Apr 30, 2023 · Jun 18, 2023
diff --git a/cypress/integration/other/configuration.spec.js b/cypress/integration/other/configuration.spec.js
@@ -125,4 +125,46 @@ describe('Configuration', () => {
       );
     });
   });
+
+  describe('suppressErrorRendering', () => {
+    beforeEach(() => {
+      cy.on('uncaught:exception', (err, runnable) => {
+        return !err.message.includes('Parse error on line');
+      });
+    });
+
+    it('should not render error diagram if suppressErrorRendering is set', () => {
+      const url = 'http://localhost:9000/suppressError.html?suppressErrorRendering=true';
+      cy.visit(url);
+      cy.window().should('have.property', 'rendered', true);
+      cy.get('#test')
+        .find('svg')
+        .should(($svg) => {
+          // all failing diagrams should not appear!
+          expect($svg).to.have.length(2);
+          // none of the diagrams should be error diagrams
+          expect($svg).to.not.contain('Syntax error');
+        });
+      cy.matchImageSnapshot(
+        'configuration.spec-should-not-render-error-diagram-if-suppressErrorRendering-is-set'
+      );
+    });
+
+    it('should render error diagram if suppressErrorRendering is not set', () => {
+      const url = 'http://localhost:9000/suppressError.html';
+      cy.visit(url);
+      cy.window().should('have.property', 'rendered', true);
+      cy.get('#test')
+        .find('svg')
+        .should(($svg) => {
+          // all five diagrams should be rendered
+          expect($svg).to.have.length(5);
+          // some of the diagrams should be error diagrams
+          expect($svg).to.contain('Syntax error');
+        });
+      cy.matchImageSnapshot(
+        'configuration.spec-should-render-error-diagram-if-suppressErrorRendering-is-not-set'
+      );
+    });
+  });
 });
diff --git a/cypress/platform/suppressError.html b/cypress/platform/suppressError.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <title>Mermaid Quick Test Page</title>
+    <link rel="icon" type="image/png" href="data:image/png;base64,iVBORw0KGgo=" />
+  </head>
+  <body>
+    <div id="test">
+      <pre class="mermaid">
+  flowchart
+      a[This should be visible]
+    </pre
+      >
+      <pre class="mermaid">
+  flowchart
+    a --< b
+    </pre
+      >
+      <pre class="mermaid">
+  flowchart
+      a[This should be visible]
+    </pre
+      >
+      <pre class="mermaid">
+  ---
+  config:
+    suppressErrorRendering: true # This should not affect anything, as suppressErrorRendering is a secure config
+  ---
+  flowchart
+    a --< b
+    </pre
+      >
+      <pre class="mermaid">
+  ---
+  config:
+    suppressErrorRendering: false # This should not affect anything, as suppressErrorRendering is a secure config
+  ---
+  flowchart
+    a --< b
+    </pre
+      >
+    </div>
+    <script type="module">
+      import mermaid from './mermaid.esm.mjs';
+      const shouldSuppress =
+        new URLSearchParams(window.location.search).get('suppressErrorRendering') === 'true';
+      mermaid.initialize({ startOnLoad: false, suppressErrorRendering: shouldSuppress });
+      try {
+        await mermaid.run();
+      } catch {
+        if (window.Cypress) {
+          window.rendered = true;
+        }
+      }
+    </script>
+  </body>
+</html>
diff --git a/docs/config/setup/modules/mermaidAPI.md b/docs/config/setup/modules/mermaidAPI.md
@@ -43,6 +43,7 @@ const config = {
   securityLevel: 'strict',
   startOnLoad: true,
   arrowMarkerAbsolute: false,
+  suppressErrorRendering: false,
 
   er: {
     diagramPadding: 20,
@@ -97,7 +98,7 @@ mermaid.initialize(config);
 
 #### Defined in
 
-[mermaidAPI.ts:622](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/mermaidAPI.ts#L622)
+[mermaidAPI.ts:635](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/mermaidAPI.ts#L635)
 
 ## Functions
 

diff --git a/packages/mermaid/src/config.type.ts b/packages/mermaid/src/config.type.ts
@@ -159,6 +159,12 @@ export interface MermaidConfig {
   dompurifyConfig?: DOMPurifyConfiguration;
   wrap?: boolean;
   fontSize?: number;
+  /**
+   * Suppresses inserting 'Syntax error' diagram in the DOM.
+   * This is useful when you want to control how to handle syntax errors in your application.
+   *
+   */
+  suppressErrorRendering?: boolean;
 }
 /**
  * The object containing configurations specific for packet diagrams.

diff --git a/packages/mermaid/src/mermaidAPI.ts b/packages/mermaid/src/mermaidAPI.ts
@@ -110,7 +110,7 @@ function processAndSetConfigs(text: string) {
  */
 async function parse(
   text: string,
-  parseOptions: ParseOptions & { suppressErrors: true }
+  parseOptions: ParseOptions & { suppressErrors: true },
 ): Promise<ParseResult | false>;
 async function parse(text: string, parseOptions?: ParseOptions): Promise<ParseResult>;
 async function parse(text: string, parseOptions?: ParseOptions): Promise<ParseResult | false> {
@@ -138,7 +138,7 @@ async function parse(text: string, parseOptions?: ParseOptions): Promise<ParseRe
 export const cssImportantStyles = (
   cssClass: string,
   element: string,
-  cssClasses: string[] = []
+  cssClasses: string[] = [],
 ): string => {
   return `\n.${cssClass} ${element} { ${cssClasses.join(' !important; ')} !important; }`;
 };
@@ -152,7 +152,7 @@ export const cssImportantStyles = (
  */
 export const createCssStyles = (
   config: MermaidConfig,
-  classDefs: Record<string, DiagramStyleClassDef> | null | undefined = {}
+  classDefs: Record<string, DiagramStyleClassDef> | null | undefined = {},
 ): string => {
   let cssStyles = '';
 
@@ -201,7 +201,7 @@ export const createUserStyles = (
   config: MermaidConfig,
   graphType: string,
   classDefs: Record<string, DiagramStyleClassDef> | undefined,
-  svgId: string
+  svgId: string,
 ): string => {
   const userCSSstyles = createCssStyles(config, classDefs);
   const allStyles = getStyles(graphType, userCSSstyles, config.themeVariables);
@@ -223,15 +223,15 @@ export const createUserStyles = (
 export const cleanUpSvgCode = (
   svgCode = '',
   inSandboxMode: boolean,
-  useArrowMarkerUrls: boolean
+  useArrowMarkerUrls: boolean,
 ): string => {
   let cleanedUpSvg = svgCode;
 
   // Replace marker-end urls with just the # anchor (remove the preceding part of the URL)
   if (!useArrowMarkerUrls && !inSandboxMode) {
     cleanedUpSvg = cleanedUpSvg.replace(
       /marker-end="url\([\d+./:=?A-Za-z-]*?#/g,
-      'marker-end="url(#'
+      'marker-end="url(#',
     );
   }
 
@@ -279,7 +279,7 @@ export const appendDivSvgG = (
   id: string,
   enclosingDivId: string,
   divStyle?: string,
-  svgXlink?: string
+  svgXlink?: string,
 ): D3Element => {
   const enclosingDiv = parentRoot.append('div');
   enclosingDiv.attr('id', enclosingDivId);
@@ -328,7 +328,7 @@ export const removeExistingElements = (
   doc: Document,
   id: string,
   divId: string,
-  iFrameId: string
+  iFrameId: string,
 ) => {
   // Remove existing SVG element if it exists
   doc.getElementById(id)?.remove();
@@ -347,7 +347,7 @@ export const removeExistingElements = (
 const render = async function (
   id: string,
   text: string,
-  svgContainingElement?: Element
+  svgContainingElement?: Element,
 ): Promise<RenderResult> {
   addDiagrams();
 
@@ -368,6 +368,16 @@ const render = async function (
   const enclosingDivID = 'd' + id;
   const enclosingDivID_selector = '#' + enclosingDivID;
 
+  const removeTempElements = () => {
+    // -------------------------------------------------------------------------------
+    // Remove the temporary HTML element if appropriate
+    const tmpElementSelector = isSandboxed ? iFrameID_selector : enclosingDivID_selector;
+    const node = select(tmpElementSelector).node();
+    if (node && 'remove' in node) {
+      node.remove();
+    }
+  };
+
   let root: any = select('body');
 
   const isSandboxed = config.securityLevel === SECURITY_LVL_SANDBOX;
@@ -424,6 +434,10 @@ const render = async function (
   try {
     diag = await Diagram.fromText(text, { title: processed.title });
   } catch (error) {
+    if (config.suppressErrorRendering) {
+      removeTempElements();
+      throw error;
+    }
     diag = await Diagram.fromText('error');
     parseEncounteredException = error;
   }
@@ -451,7 +465,11 @@ const render = async function (
   try {
     await diag.renderer.draw(text, id, version, diag);
   } catch (e) {
-    errorRenderer.draw(text, id, version);
+    if (config.suppressErrorRendering) {
+      removeTempElements();
+    } else {
+      errorRenderer.draw(text, id, version);
+    }
     throw e;
   }
 
@@ -487,13 +505,7 @@ const render = async function (
     throw parseEncounteredException;
   }
 
-  // -------------------------------------------------------------------------------
-  // Remove the temporary HTML element if appropriate
-  const tmpElementSelector = isSandboxed ? iFrameID_selector : enclosingDivID_selector;
-  const node = select(tmpElementSelector).node();
-  if (node && 'remove' in node) {
-    node.remove();
-  }
+  removeTempElements();
 
   return {
     diagramType,
@@ -520,7 +532,7 @@ function initialize(options: MermaidConfig = {}) {
   if (options?.theme && options.theme in theme) {
     // Todo merge with user options
     options.themeVariables = theme[options.theme as keyof typeof theme].getThemeVariables(
-      options.themeVariables
+      options.themeVariables,
     );
   } else if (options) {
     options.themeVariables = theme.default.getThemeVariables(options.themeVariables);
@@ -550,7 +562,7 @@ function addA11yInfo(
   diagramType: string,
   svgNode: D3Element,
   a11yTitle?: string,
-  a11yDescr?: string
+  a11yDescr?: string,
 ): void {
   setA11yDiagramInfo(svgNode, diagramType);
   addSVGa11yTitleDescription(svgNode, a11yTitle, a11yDescr, svgNode.attr('id'));
@@ -566,6 +578,7 @@ function addA11yInfo(
  *     securityLevel: 'strict',
  *     startOnLoad: true,
  *     arrowMarkerAbsolute: false,
+ *     suppressErrorRendering: false,
  *
  *     er: {
  *       diagramPadding: 20,

diff --git a/packages/mermaid/src/schemas/config.schema.yaml b/packages/mermaid/src/schemas/config.schema.yaml
@@ -159,7 +159,15 @@ properties:
       in the current `currentConfig`.
 
       This prevents malicious graph directives from overriding a site's default security.
-    default: ['secure', 'securityLevel', 'startOnLoad', 'maxTextSize', 'maxEdges']
+    default:
+      [
+        'secure',
+        'securityLevel',
+        'startOnLoad',
+        'maxTextSize',
+        'suppressErrorRendering',
+        'maxEdges',
+      ]
     type: array
     items:
       type: string
@@ -235,6 +243,12 @@ properties:
   fontSize:
     type: number
     default: 16
+  suppressErrorRendering:
+    type: boolean
+    default: false
+    description: |
+      Suppresses inserting 'Syntax error' diagram in the DOM.
+      This is useful when you want to control how to handle syntax errors in your application.
 
 $defs: # JSON Schema definition (maybe we should move these to a separate file)
   BaseDiagramConfig: