Add "ignore" option

README.md

@@ -266,6 +266,32 @@ _The import map to extend._
 
 An initial import map to start with - can be from a previous install or provide custom mappings.
 
+#### ignore
+
+> Type: string[] | undefined<br/>
+Default: []
+
+Allows ignoring certain module specifiers during the tracing process.
+It can be useful, for example, when you provide an `inputMap` that contains a mapping that can't be traced in current context,
+but you know it will work in the context where the generated map is going to be used.
+
+```js
+const generator = new Generator({
+  inputMap: {
+      imports: {
+          "react": "./my/own/react.js",
+      }
+  },
+  ignore: ["react"]
+});
+
+// Even though `@react-three/fiber@7` depends upon `react`,
+// `generator` will not try to trace and resolve `react`,
+// so the mapping provided in `inputMap` will end up in the resulting import map. 
+await generator.install("@react-three/fiber@7")
+```
+
+
 #### defaultProvider
 
 > Type: 'jspm' | 'jspm.system' | 'nodemodules' | 'skypack' | 'jsdelivr' | 'unpkg'<br/>

src/generator.ts

@@ -23,6 +23,10 @@ export interface GeneratorOptions {
   stdlib?: string;
   customProviders?: Record<string, Provider>;
   providers?: Record<string, string>;
+  /**
+   * List of module specifiers to ignore during tracing.
+   */
+  ignore?: string[];
 }
 
 export interface ModuleAnalysis {
@@ -61,7 +65,8 @@ export class Generator {
     customProviders = undefined,
     providers = {},
     cache = true,
-    stdlib = '@jspm/core'
+    stdlib = '@jspm/core',
+    ignore = []
   }: GeneratorOptions = {}) {
     let fetchOpts = undefined;
     if (cache === 'offline')
@@ -90,7 +95,8 @@ export class Generator {
       env,
       defaultProvider,
       providers,
-      inputMap
+      inputMap,
+      ignore
     }, log, resolver);
   }
 

src/trace/tracemap.ts

@@ -21,6 +21,9 @@ export interface TraceMapOptions extends InstallOptions {
   // or an exact trace for the provided entry points
   // (currently unused)
   fullMap?: boolean;
+
+  // List of module specifiers to ignore during tracing
+  ignore?: string[]
 }
 
 interface TraceGraph {
@@ -125,7 +128,7 @@ export default class TraceMap {
             const [specifier, parentUrl] = trace.split('##');
             try {
               const resolved = await this.trace(specifier, new URL(parentUrl), this.tracedUrls?.[parentUrl]?.wasCJS ? ['require', ...this.env] : ['import', ...this.env]);
-              traceResolutions[trace] = resolved;
+              if (resolved) traceResolutions[trace] = resolved;
             }
             catch (e) {
               throw e;
@@ -207,7 +210,13 @@ export default class TraceMap {
   //   }
   // }
 
-  async trace (specifier: string, parentUrl = this.mapBase, env = ['import', ...this.env]): Promise<string> {
+  /**
+   * @returns `resolved` - either a URL `string` pointing to the module or `null` if the specifier should be ignored.
+   */
+  async trace (specifier: string, parentUrl = this.mapBase, env = ['import', ...this.env]): Promise<string | null> {
+    // TODO: support ignoring prefixes?
+    if (this.opts.ignore?.includes(specifier)) return null
+
     const parentPkgUrl = await this.resolver.getPackageBase(parentUrl.href);
     if (!parentPkgUrl)
       throwInternalError();
@@ -365,6 +374,8 @@ export default class TraceMap {
         return;
       }
       const resolved = await this.trace(dep, resolvedUrlObj, env);
+      if (resolved === null) return
+
       if (deps.includes(dep))
         traceEntry.deps[dep] = resolved;
       if (dynamicDeps.includes(dep))

test/api/ignore.test.js

@@ -0,0 +1,41 @@
+import { Generator } from '@jspm/generator';
+import assert from 'assert';
+
+const generator = new Generator({
+  mapUrl: import.meta.url,
+  inputMap: {
+    "imports": {
+      "react": "./location/that/cant/be/traced.js"
+    }
+  },
+  ignore: ['react'],
+  env: ['production', 'browser', 'module']
+});
+
+await generator.install('@react-three/fiber@7.0.15')
+
+const json = generator.getMap();
+
+console.log(json)
+
+assert.deepEqual(json, {
+  "imports": {
+    "react": "./location/that/cant/be/traced.js",
+    "@react-three/fiber": "https://ga.jspm.io/npm:@react-three/fiber@7.0.15/dist/react-three-fiber.esm.js",
+  },
+  "scopes": {
+    "https://ga.jspm.io/": {
+      "debounce": "https://ga.jspm.io/npm:debounce@1.2.1/index.js",
+      "fast-deep-equal": "https://ga.jspm.io/npm:fast-deep-equal@3.1.3/index.js",
+      "object-assign": "https://ga.jspm.io/npm:object-assign@4.1.1/index.js",
+      "react-merge-refs": "https://ga.jspm.io/npm:react-merge-refs@1.1.0/dist/index.js",
+      "react-reconciler": "https://ga.jspm.io/npm:react-reconciler@0.26.2/index.js",
+      "react-use-measure": "https://ga.jspm.io/npm:react-use-measure@2.0.4/dist/web.cjs.js",
+      "scheduler": "https://ga.jspm.io/npm:scheduler@0.20.2/index.js",
+      "three": "https://ga.jspm.io/npm:three@0.133.1/build/three.module.js",
+      "use-asset": "https://ga.jspm.io/npm:use-asset@1.0.4/dist/index.cjs.js",
+      "zustand": "https://ga.jspm.io/npm:zustand@3.5.13/esm/index.js",
+      "zustand/shallow": "https://ga.jspm.io/npm:zustand@3.5.13/esm/shallow.js"
+    }
+  }
+});