feat(ses): Support dynamic import

Author: kriskowal

packages/ses/NEWS.md

@@ -2,7 +2,11 @@ User-visible changes in `ses`:
 
 # Next version
 
-- Specifying the long discontinued `mathTaming` or `dateTaming` options logs a warning.
+- Adds support for dynamic `import` in conjunction with an update to
+  `@endo/module-source`.
+
+- Specifying the long-discontinued `mathTaming` or `dateTaming` options logs a
+  warning.
 
 # v1.10.0 (2024-11-13)
 

packages/ses/src/compartment.js

@@ -19,15 +19,15 @@ import {
   setGlobalObjectMutableProperties,
   setGlobalObjectEvaluators,
 } from './global-object.js';
-import { assert, assertEqual } from './error/assert.js';
+import { assert, assertEqual, q } from './error/assert.js';
 import { sharedGlobalPropertyNames } from './permits.js';
 import { load, loadNow } from './module-load.js';
 import { link } from './module-link.js';
 import { getDeferredExports } from './module-proxy.js';
 import { compartmentEvaluate } from './compartment-evaluate.js';
 import { makeSafeEvaluator } from './make-safe-evaluator.js';
 
-/** @import {ModuleDescriptor} from '../types.js' */
+/** @import {ModuleDescriptor, ModuleExportsNamespace} from '../types.js' */
 
 // moduleAliases associates every public module exports namespace with its
 // corresponding compartment and specifier so they can be used to link modules
@@ -297,6 +297,43 @@ export const makeCompartmentConstructor = (
 
     assign(globalObject, endowments);
 
+    /**
+     * In support dynamic import in a module source loaded by this compartment,
+     * like `await import(importSpecifier)`, induces this compartment to import
+     * a module, returning a promise for the resulting module exports
+     * namespace.
+     * Unlike `compartment.import`, never creates a box object for the
+     * namespace as that behavior is deprecated and inconsistent with the
+     * standard behavior of dynamic import.
+     * Obliges the caller to resolve import specifiers to their corresponding
+     * full specifier.
+     * That is, every module must have its own dynamic import function that
+     * closes over the surrounding module's full module specifier and calls
+     * through to this function.
+     * @param {string} fullSpecifier - A full specifier is a key in the
+     * compartment's module memo.
+     * The method `compartment.import` accepts a full specifier, but dynamic
+     * import accepts an import specifier and resolves it to a full specifier
+     * relative to the calling module's full specifier.
+     * @returns {Promise<ModuleExportsNamespace>}
+     */
+    const compartmentImport = async fullSpecifier => {
+      if (typeof resolveHook !== 'function') {
+        throw new TypeError(
+          `Compartment does not support dynamic import: no configured resolveHook for compartment ${q(name)}`,
+        );
+      }
+      await load(privateFields, moduleAliases, this, fullSpecifier);
+      const { execute, exportsProxy } = link(
+        privateFields,
+        moduleAliases,
+        this,
+        fullSpecifier,
+      );
+      execute();
+      return exportsProxy;
+    };
+
     weakmapSet(privateFields, this, {
       name: `${name}`,
       globalTransforms,
@@ -314,6 +351,7 @@ export const makeCompartmentConstructor = (
       instances,
       parentCompartment,
       noNamespaceBox,
+      compartmentImport,
     });
   }
 

packages/ses/src/module-instance.js

@@ -1,3 +1,5 @@
+/** @import {ModuleExportsNamespace} from '../types.js' */
+
 import { assert } from './error/assert.js';
 import { getDeferredExports } from './module-proxy.js';
 import {
@@ -131,13 +133,15 @@ export const makeModuleInstance = (
     __fixedExportMap__: fixedExportMap = {},
     __liveExportMap__: liveExportMap = {},
     __reexportMap__: reexportMap = {},
+    __needsImport__: needsImport = false,
     __needsImportMeta__: needsImportMeta = false,
     __syncModuleFunctor__,
   } = moduleSource;
 
   const compartmentFields = weakmapGet(privateFields, compartment);
 
-  const { __shimTransforms__, importMetaHook } = compartmentFields;
+  const { __shimTransforms__, resolveHook, importMetaHook, compartmentImport } =
+    compartmentFields;
 
   const { exportsProxy, exportsTarget, activate } = getDeferredExports(
     compartment,
@@ -171,6 +175,14 @@ export const makeModuleInstance = (
     importMetaHook(moduleSpecifier, importMeta);
   }
 
+  /** @type {(fullSpecifier: string) => Promise<ModuleExportsNamespace>} */
+  let dynamicImport;
+  if (needsImport) {
+    /** @param {string} importSpecifier */
+    dynamicImport = async importSpecifier =>
+      compartmentImport(resolveHook(importSpecifier, moduleSpecifier));
+  }
+
   // {_localName_: [{get, set, notify}]} used to merge all the export updaters.
   const localGetNotify = create(null);
 
@@ -462,6 +474,7 @@ export const makeModuleInstance = (
             imports: freeze(imports),
             onceVar: freeze(onceVar),
             liveVar: freeze(liveVar),
+            import: dynamicImport,
             importMeta,
           }),
         );

packages/ses/test/import.test.js

@@ -4,6 +4,7 @@
 /* eslint max-lines: 0 */
 
 import test from 'ava';
+import { ModuleSource } from '@endo/module-source';
 import '../index.js';
 import { resolveNode, makeNodeImporter } from './_node.js';
 import { makeImporter, makeStaticRetriever } from './_import-commons.js';
@@ -600,3 +601,21 @@ test('importMetaHook and meta from record', async t => {
   const { default: metaurl } = await compartment.import('./index.js');
   t.is(metaurl, 'https://example.com/index.js?foo');
 });
+
+test('dynamic import from source', async t => {
+  const c = new Compartment({
+    __options__: true,
+    __noNamespaceBox__: true,
+    resolveHook: s => s,
+    modules: {
+      '-': {
+        source: new ModuleSource(`
+          export const dynamic = import('-');
+        `),
+      },
+    },
+  });
+  const namespace = await c.import('-');
+  const namespace2 = await namespace.dynamic;
+  t.is(namespace, namespace2);
+});