mermaid

public/client.js

@@ -64,41 +64,6 @@ function recommendedLibraries() {
     html: () => import("https://cdn.jsdelivr.net/npm/htl/+esm").then((htl) => htl.html),
     svg: () => import("https://cdn.jsdelivr.net/npm/htl/+esm").then((htl) => htl.svg),
     Plot: () => import("https://cdn.jsdelivr.net/npm/@observablehq/plot/+esm"),
-    dot: async () => {
-      // TODO Incorporate this into the standard library.
-      const viz = await import("https://cdn.jsdelivr.net/npm/@viz-js/viz/+esm").then(({instance}) => instance());
-      return function dot(strings) {
-        let string = strings[0] + "";
-        let i = 0;
-        let n = arguments.length;
-        while (++i < n) string += arguments[i] + "" + strings[i];
-        const svg = viz.renderSVGElement(string, {
-          graphAttributes: {
-            bgcolor: "none"
-          },
-          nodeAttributes: {
-            color: "#00000101",
-            fontcolor: "#00000101",
-            fontname: "var(--sans-serif)",
-            fontsize: "12"
-          },
-          edgeAttributes: {
-            color: "#00000101"
-          }
-        });
-        for (const e of svg.querySelectorAll("[stroke='#000001'][stroke-opacity='0.003922']")) {
-          e.setAttribute("stroke", "currentColor");
-          e.removeAttribute("stroke-opacity");
-        }
-        for (const e of svg.querySelectorAll("[fill='#000001'][fill-opacity='0.003922']")) {
-          e.setAttribute("fill", "currentColor");
-          e.removeAttribute("fill-opacity");
-        }
-        svg.remove();
-        svg.style = "max-width: 100%; height: auto;";
-        return svg;
-      };
-    },
     Inputs: () => {
       // TODO Observable Inputs needs to include the CSS in the dist folder
       // published to npm, and we should replace the __ns__ namespace with
@@ -109,7 +74,60 @@ function recommendedLibraries() {
       link.href = "https://cdn.jsdelivr.net/gh/observablehq/inputs/src/style.css";
       document.head.append(link);
       return inputs;
+    },
+    dot,
+    mermaid
+  };
+}
+
+// TODO Incorporate this into the standard library.
+async function dot() {
+  const {instance} = await import("https://cdn.jsdelivr.net/npm/@viz-js/viz/+esm");
+  const viz = await instance();
+  return function dot(strings) {
+    let string = strings[0] + "";
+    let i = 0;
+    let n = arguments.length;
+    while (++i < n) string += arguments[i] + "" + strings[i];
+    const svg = viz.renderSVGElement(string, {
+      graphAttributes: {
+        bgcolor: "none"
+      },
+      nodeAttributes: {
+        color: "#00000101",
+        fontcolor: "#00000101",
+        fontname: "var(--sans-serif)",
+        fontsize: "12"
+      },
+      edgeAttributes: {
+        color: "#00000101"
+      }
+    });
+    for (const e of svg.querySelectorAll("[stroke='#000001'][stroke-opacity='0.003922']")) {
+      e.setAttribute("stroke", "currentColor");
+      e.removeAttribute("stroke-opacity");
     }
+    for (const e of svg.querySelectorAll("[fill='#000001'][fill-opacity='0.003922']")) {
+      e.setAttribute("fill", "currentColor");
+      e.removeAttribute("fill-opacity");
+    }
+    svg.remove();
+    svg.style = "max-width: 100%; height: auto;";
+    return svg;
+  };
+}
+
+// TODO Incorporate this into the standard library.
+async function mermaid() {
+  let nextId = 0;
+  const {default: mer} = await import("https://cdn.jsdelivr.net/npm/mermaid/+esm");
+  mer.initialize({startOnLoad: false, securityLevel: "loose", theme: "neutral"});
+  return async function mermaid() {
+    const div = document.createElement("div");
+    div.innerHTML = (await mer.render(`mermaid-${++nextId}`, String.raw.apply(String, arguments))).svg;
+    const svg = div.firstChild;
+    svg.remove();
+    return svg;
   };
 }
 

src/markdown.ts

@@ -87,6 +87,8 @@ function getLiveSource(content, language, option) {
     ? transpileTag(content, "tex.block", true)
     : language === "dot"
     ? transpileTag(content, "dot", false)
+    : language === "mermaid"
+    ? transpileTag(content, "await mermaid", false)
     : undefined;
 }
 

src/render.ts

@@ -115,11 +115,12 @@ function getImportPreloads(parseResult: ParseResult): Iterable<string> {
   const specifiers = new Set<string>(["npm:@observablehq/runtime"]);
   for (const {name} of parseResult.imports) specifiers.add(name);
   const inputs = new Set(parseResult.cells.flatMap((cell) => cell.inputs ?? []));
-  if (inputs.has("dot")) specifiers.add("npm:@viz-js/viz");
   if (inputs.has("d3") || inputs.has("Plot")) specifiers.add("npm:d3");
   if (inputs.has("Plot")) specifiers.add("npm:@observablehq/plot");
   if (inputs.has("htl") || inputs.has("html") || inputs.has("svg") || inputs.has("Inputs")) specifiers.add("npm:htl");
   if (inputs.has("Inputs")) specifiers.add("npm:@observablehq/inputs");
+  if (inputs.has("dot")) specifiers.add("npm:@viz-js/viz");
+  if (inputs.has("mermaid")) specifiers.add("npm:mermaid").add("npm:d3");
   const preloads: string[] = [];
   for (const specifier of specifiers) {
     const resolved = resolveImport(specifier);

test/input/mermaid.md

@@ -0,0 +1,7 @@
+```mermaid
+graph TD;
+    A-->B;
+    A-->C;
+    B-->D;
+    C-->D;
+```

test/output/mermaid.html

@@ -0,0 +1 @@
+<div id="cell-1ffa6d4f" class="observablehq observablehq--block"></div>

test/output/mermaid.json

@@ -0,0 +1,27 @@
+{
+  "data": null,
+  "title": null,
+  "files": [],
+  "imports": [],
+  "pieces": [
+    {
+      "type": "html",
+      "id": "",
+      "cellIds": [
+        "1ffa6d4f"
+      ],
+      "html": "<div id=\"cell-1ffa6d4f\" class=\"observablehq observablehq--block\"></div>\n"
+    }
+  ],
+  "cells": [
+    {
+      "type": "cell",
+      "id": "1ffa6d4f",
+      "inputs": [
+        "mermaid",
+        "display"
+      ],
+      "body": "async (mermaid,display) => {\ndisplay((\nawait mermaid`graph TD;\n    A-->B;\n    A-->C;\n    B-->D;\n    C-->D;\n`\n))\n}"
+    }
+  ]
+}