feat(mermaid): start implementing a basic linter

src/public/app/types.d.ts

@@ -207,6 +207,8 @@ declare global {
         modeInfo: ModeInfo[];
         findModeByMIME(mime: string): ModeInfo;
         autoLoadMode(instance: CodeMirrorInstance, mode: string)
+        registerHelper(type: string, filter: string | null, callback: (text: string, options: object) => unknown);
+        Pos(line: number, col: number);
     }
 
     interface ModeInfo {

src/public/app/widgets/type_widgets/linters/mermaid.ts

@@ -0,0 +1,43 @@
+import mermaid from "mermaid";
+
+interface MermaidParseError extends Error {
+    hash: {
+        text: string;
+        token: string;
+        line: number;
+        loc: {
+            first_line: number;
+            first_column: number;
+            last_line: number;
+            last_column: number;
+        };
+        expected: string[]
+    }
+}
+
+export default function registerErrorReporter() {
+    CodeMirror.registerHelper("lint", null, (async (text, options) => {
+        if (!text.trim()) {
+            return [];
+        }
+
+        try {
+            await mermaid.parse(text);
+        } catch (e: unknown) {
+            console.warn("Got validation error", JSON.stringify(e));
+
+            const mermaidError = (e as MermaidParseError);
+            const loc = mermaidError.hash.loc;
+            return [
+                {
+                    message: mermaidError.message,
+                    severity: "error",
+                    from: CodeMirror.Pos(loc.first_line - 1, loc.first_column - 1),
+                    to: CodeMirror.Pos(loc.last_line - 1, loc.last_column - 1)
+                }
+            ];
+        }
+
+        return [];
+    }));
+}

src/public/app/widgets/type_widgets/mermaid.ts

@@ -1,9 +1,9 @@
 import type { MermaidConfig } from "mermaid";
-import library_loader from "../../services/library_loader.js";
 import { loadElkIfNeeded, postprocessMermaidSvg } from "../../services/mermaid.js";
 import AbstractSvgSplitTypeWidget from "./abstract_svg_split_type_widget.js";
 
 let idCounter = 1;
+let registeredErrorReporter = false;
 
 export class MermaidTypeWidget extends AbstractSvgSplitTypeWidget {
 
@@ -14,19 +14,29 @@ export class MermaidTypeWidget extends AbstractSvgSplitTypeWidget {
     async renderSvg(content: string) {
         const mermaid = (await import("mermaid")).default;
         await loadElkIfNeeded(mermaid, content);
+        if (!registeredErrorReporter) {
+            (await import("./linters/mermaid.js")).default();
+            registeredErrorReporter = true;
+        }
 
-        mermaid.mermaidAPI.initialize({
+        mermaid.initialize({
             startOnLoad: false,
-            ...(getMermaidConfig() as any)
+            ...(getMermaidConfig() as any),
         });
 
         idCounter++;
-        const { svg } = await mermaid.mermaidAPI.render(`mermaid-graph-${idCounter}`, content);
-        return postprocessMermaidSvg(svg);
+        try {
+            const { svg } = await mermaid.render(`mermaid-graph-${idCounter}`, content);
+            return postprocessMermaidSvg(svg);
+        } catch (e) {
+            console.warn(JSON.stringify(e));
+            return "";
+        }
     }
 
 }
 
+
 export function getMermaidConfig(): MermaidConfig {
     const documentStyle = window.getComputedStyle(document.documentElement);
     const mermaidTheme = documentStyle.getPropertyValue("--mermaid-theme") as "default";