Improve warning for multiple loads

Ref: #2034

CHANGELOG.md

@@ -793,6 +793,10 @@
 
 ## v0.20.31 (2021-03-14)
 
+### Features
+
+-   Improved warning message if TypeDoc is loaded multiple times.
+
 ### Bug Fixes
 
 -   readonly tuples were recognized as arrays, closes #1534

scripts/accept_visual_regression.js

@@ -1,12 +1,13 @@
 //@ts-check
 
-const { remove, copy } = require("../dist/lib/utils/fs");
+const fs = require("fs/promises");
+const { copy } = require("../dist/lib/utils/fs");
 const { join } = require("path");
 
 const expectedDir = join(__dirname, "../dist/tmp/.reg/expected");
 const outputDir = join(__dirname, "../dist/tmp/__screenshots__");
 
-remove(expectedDir)
+fs.rmdir(expectedDir, { recursive: true })
     .then(() => copy(outputDir, expectedDir))
     .catch((err) => {
         console.error(err);

src/lib/application.ts

@@ -31,7 +31,7 @@ import {
     getWatchEntryPoints,
 } from "./utils/entry-point";
 import { nicePath } from "./utils/paths";
-import { hasBeenLoadedMultipleTimes } from "./utils/general";
+import { getLoadedPaths, hasBeenLoadedMultipleTimes } from "./utils/general";
 import { validateExports } from "./validation/exports";
 import { validateDocumentation } from "./validation/documentation";
 import { validateLinks } from "./validation/links";
@@ -152,7 +152,9 @@ export class Application extends ChildableComponent<
 
         if (hasBeenLoadedMultipleTimes()) {
             this.logger.warn(
-                `TypeDoc has been loaded multiple times. This is commonly caused by plugins which have their own installation of TypeDoc. This will likely break things.`
+                `TypeDoc has been loaded multiple times. This is commonly caused by plugins which have their own installation of TypeDoc. The loaded paths are:\n\t${getLoadedPaths().join(
+                    "\n\t"
+                )}`
             );
         }
     }

src/lib/utils/general.ts

@@ -1,3 +1,4 @@
+import { dirname } from "path";
 import * as Util from "util";
 
 /**
@@ -59,11 +60,23 @@ export function assertNever(x: never): never {
  * multiple times, then parts of it will not work as expected.
  */
 const loadSymbol = Symbol.for("typedoc_loads");
-const getLoads = () => globalThis[loadSymbol as never] || 0;
+const pathSymbol = Symbol.for("typedoc_paths");
 
-// @ts-expect-error there's no way to add symbols to globalThis, sadly.
-globalThis[loadSymbol] = getLoads() + 1;
+interface TypeDocGlobals {
+    [loadSymbol]?: number;
+    [pathSymbol]?: string[];
+}
+const g = globalThis as TypeDocGlobals;
+
+g[loadSymbol] = (g[loadSymbol] || 0) + 1;
+g[pathSymbol] ||= [];
+// transform /abs/path/to/typedoc/dist/lib/utils/general -> /abs/path/to/typedoc
+g[pathSymbol].push(dirname(dirname(dirname(__dirname))));
 
 export function hasBeenLoadedMultipleTimes() {
-    return getLoads() !== 1;
+    return g[loadSymbol] !== 1;
+}
+
+export function getLoadedPaths() {
+    return g[pathSymbol] || [];
 }