plugins can export importLoader for use with --import

src/test/package.json

@@ -51,6 +51,7 @@
     "typedoc": "typedoc --tsconfig tsconfig/esm.json ./src/*.ts"
   },
   "tap": {
+    "typecheck": false,
     "coverage-map": "map.js"
   },
   "peerDependencies": {

src/test/scripts/build.mts

@@ -53,8 +53,16 @@ const seen = new Set<string>()
 // raise an error and do not continue.
 const hasConfig = new Map<string, string>()
 const hasPlugin = new Map<string, string>()
+
+// has a loader, and no importLoader
 const hasLoader = new Map<string, string>()
+// has an importLoader
+const hasImport = new Map<string, string>()
+// the loader export, if an importLoader is present
+const hasLoaderFallback = new Map<string, string>()
+
 const preloaders = new Map<string, string>()
+const preimports = new Map<string, string>()
 const testFileExtensions = new Set<string>()
 
 const signature = plugins
@@ -85,6 +93,7 @@ const pluginNames = plugins.map(p => {
       >
     }
     loader?: string
+    importLoader?: string
     preload?: boolean
     testFileExtensions?: string[]
   }
@@ -128,9 +137,15 @@ const pluginNames = plugins.map(p => {
     hasPlugin.set(p, name)
     isPlugin = true
   }
+  if (typeof imp.importLoader === 'string') {
+    if (imp.preload === true) preimports.set(p, imp.importLoader)
+    hasImport.set(p, imp.importLoader)
+    isPlugin = true
+  }
   if (typeof imp.loader === 'string') {
-    hasLoader.set(p, imp.loader)
     if (imp.preload === true) preloaders.set(p, imp.loader)
+    if (!imp.importLoader) hasLoader.set(p, imp.loader)
+    else hasLoaderFallback.set(p, imp.loader)
     isPlugin = true
   }
   if (!isPlugin) {
@@ -243,6 +258,12 @@ const pluginLoaders = `const preloaders = new Set<string>(${JSON.stringify(
   2
 )})
 
+const preimports = new Set<string>(${JSON.stringify(
+  [...preimports.values()],
+  null,
+  2
+)})
+
 /**
  * The set of \`loader\` strings exported by plugins. If a plugin exports
  * \`preload = true\`, then it will be sorted to the start of this list, so
@@ -253,8 +274,39 @@ export const loaders: string[] = ${JSON.stringify(
   null,
   2
 )}.sort(
-  (a, b) => preloaders.has(a) ? -1 : preloaders.has(b) ? 1 : 0
+  (a, b) => preloaders.has(a) && !preloaders.has(b) ? -1
+    : !preloaders.has(a) && preloaders.has(b) ? 1
+    : 0
 )
+
+/**
+ * The set of \`importLoader\` strings exported by plugins, for use with
+ * \`Module.register\` in node v20.6 and higher.
+ */
+export const importLoaders: string[] = ${JSON.stringify(
+  [...hasImport.values()],
+  null,
+  2
+)}.sort(
+  (a, b) => preimports.has(a) && !preimports.has(b) ? -1
+    : !preimports.has(a) && preimports.has(b) ? 1
+    : 0
+)
+
+/**
+ * All \`loader\` strings exported by plugins, including fallbacks provided
+ * for those that also export an \`importLoader\`
+ */
+export const loaderFallbacks: string[] = ${JSON.stringify(
+  [...hasLoaderFallback.values()].concat([...hasLoader.values()]),
+  null,
+  2
+)}.sort(
+  (a, b) => preloaders.has(a) && !preloaders.has(b) ? -1
+    : !preloaders.has(a) && preloaders.has(b) ? 1
+    : 0
+)
+
 `
 
 const testFileExtensionsCode = [...testFileExtensions]

src/test/scripts/test-template.ts

@@ -175,7 +175,12 @@ c
 //{{PLUGINS CONFIG END}}
 
 //{{LOADERS START}}
+// these are always added with --loader
 export const loaders = []
+// these are added with --import, if available
+export const importLoaders = []
+// these are added with --loader, only if --import is unavailable
+export const loaderFallbacks = []
 //{{LOADERS END}}
 
 /**

src/test/test-built/dist/cjs/index.d.ts

@@ -212,6 +212,16 @@ export declare const config: <C extends ConfigSet>(jack: Jack<C>) => Jack<C & im
  * that Node loads it before other loaders.
  */
 export declare const loaders: string[];
+/**
+ * The set of `importLoader` strings exported by plugins, for use with
+ * `Module.register` in node v20.6 and higher.
+ */
+export declare const importLoaders: string[];
+/**
+ * All `loader` strings exported by plugins, including fallbacks provided
+ * for those that also export an `importLoader`
+ */
+export declare const loaderFallbacks: string[];
 /**
  * The string signature that lists all loaded plugins alphabetically, used
  * to determine whether a rebuild is necessary by comparing it to the `plugin`

src/test/test-built/dist/mjs/index.d.ts

@@ -212,6 +212,16 @@ export declare const config: <C extends ConfigSet>(jack: Jack<C>) => Jack<C & im
  * that Node loads it before other loaders.
  */
 export declare const loaders: string[];
+/**
+ * The set of `importLoader` strings exported by plugins, for use with
+ * `Module.register` in node v20.6 and higher.
+ */
+export declare const importLoaders: string[];
+/**
+ * All `loader` strings exported by plugins, including fallbacks provided
+ * for those that also export an `importLoader`
+ */
+export declare const loaderFallbacks: string[];
 /**
  * The string signature that lists all loaded plugins alphabetically, used
  * to determine whether a rebuild is necessary by comparing it to the `plugin`