sea: implement sea.getAssetKeys()

This adds a new API to allow the bundled script in SEA to query
the list of assets.

PR-URL: https://github.com/nodejs/node/pull/59661
Refs: https://github.com/nodejs/single-executable/discussions/112
Reviewed-By: Darshan Sen <raisinten@gmail.com>

doc/api/single-executable-applications.md

@@ -221,7 +221,10 @@ executable, users can retrieve the assets using the [`sea.getAsset()`][] and
 The single-executable application can access the assets as follows:
 
 ```cjs
-const { getAsset, getAssetAsBlob, getRawAsset } = require('node:sea');
+const { getAsset, getAssetAsBlob, getRawAsset, getAssetKeys } = require('node:sea');
+// Get all asset keys.
+const keys = getAssetKeys();
+console.log(keys); // ['a.jpg', 'b.txt']
 // Returns a copy of the data in an ArrayBuffer.
 const image = getAsset('a.jpg');
 // Returns a string decoded from the asset as UTF8.
@@ -232,8 +235,8 @@ const blob = getAssetAsBlob('a.jpg');
 const raw = getRawAsset('a.jpg');
 ```
 
-See documentation of the [`sea.getAsset()`][], [`sea.getAssetAsBlob()`][] and [`sea.getRawAsset()`][]
-APIs for more information.
+See documentation of the [`sea.getAsset()`][], [`sea.getAssetAsBlob()`][],
+[`sea.getRawAsset()`][] and [`sea.getAssetKeys()`][] APIs for more information.
 
 ### Startup snapshot support
 
@@ -429,6 +432,19 @@ writes to the returned array buffer is likely to result in a crash.
   `assets` field in the single-executable application configuration.
 * Returns: {ArrayBuffer}
 
+### `sea.getAssetKeys()`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns {string\[]} An array containing all the keys of the assets
+  embedded in the executable. If no assets are embedded, returns an empty array.
+
+This method can be used to retrieve an array of all the keys of assets
+embedded into the single-executable application.
+An error is thrown when not running inside a single-executable application.
+
 ### `require(id)` in the injected main script is not file based
 
 `require()` in the injected main script is not the same as the [`require()`][]
@@ -503,6 +519,7 @@ to help us document them.
 [`require.main`]: modules.md#accessing-the-main-module
 [`sea.getAsset()`]: #seagetassetkey-encoding
 [`sea.getAssetAsBlob()`]: #seagetassetasblobkey-options
+[`sea.getAssetKeys()`]: #seagetassetkeys
 [`sea.getRawAsset()`]: #seagetrawassetkey
 [`v8.startupSnapshot.setDeserializeMainFunction()`]: v8.md#v8startupsnapshotsetdeserializemainfunctioncallback-data
 [`v8.startupSnapshot` API]: v8.md#startup-snapshot-api

lib/sea.js

@@ -3,7 +3,7 @@ const {
   ArrayBufferPrototypeSlice,
 } = primordials;
 
-const { isSea, getAsset: getAssetInternal } = internalBinding('sea');
+const { isSea, getAsset: getAssetInternal, getAssetKeys: getAssetKeysInternal } = internalBinding('sea');
 const { TextDecoder } = require('internal/encoding');
 const { validateString } = require('internal/validators');
 const {
@@ -68,9 +68,23 @@ function getAssetAsBlob(key, options) {
   return new Blob([asset], options);
 }
 
+/**
+ * Returns an array of all the keys of assets embedded into the
+ * single-executable application.
+ * @returns {string[]}
+ */
+function getAssetKeys() {
+  if (!isSea()) {
+    throw new ERR_NOT_IN_SINGLE_EXECUTABLE_APPLICATION();
+  }
+
+  return getAssetKeysInternal() || [];
+}
+
 module.exports = {
   isSea,
   getAsset,
   getRawAsset,
   getAssetAsBlob,
+  getAssetKeys,
 };

src/node_sea.cc

@@ -29,6 +29,7 @@
 #include <vector>
 
 using node::ExitCode;
+using v8::Array;
 using v8::ArrayBuffer;
 using v8::BackingStore;
 using v8::Context;
@@ -807,6 +808,25 @@ void GetAsset(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(ab);
 }
 
+void GetAssetKeys(const FunctionCallbackInfo<Value>& args) {
+  CHECK_EQ(args.Length(), 0);
+  Isolate* isolate = args.GetIsolate();
+  SeaResource sea_resource = FindSingleExecutableResource();
+
+  Local<Context> context = isolate->GetCurrentContext();
+  LocalVector<Value> keys(isolate);
+  keys.reserve(sea_resource.assets.size());
+  for (const auto& [key, _] : sea_resource.assets) {
+    Local<Value> key_str;
+    if (!ToV8Value(context, key).ToLocal(&key_str)) {
+      return;
+    }
+    keys.push_back(key_str);
+  }
+  Local<Array> result = Array::New(isolate, keys.data(), keys.size());
+  args.GetReturnValue().Set(result);
+}
+
 MaybeLocal<Value> LoadSingleExecutableApplication(
     const StartExecutionCallbackInfo& info) {
   // Here we are currently relying on the fact that in NodeMainInstance::Run(),
@@ -858,12 +878,14 @@ void Initialize(Local<Object> target,
             "isExperimentalSeaWarningNeeded",
             IsExperimentalSeaWarningNeeded);
   SetMethod(context, target, "getAsset", GetAsset);
+  SetMethod(context, target, "getAssetKeys", GetAssetKeys);
 }
 
 void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(IsSea);
   registry->Register(IsExperimentalSeaWarningNeeded);
   registry->Register(GetAsset);
+  registry->Register(GetAssetKeys);
 }
 
 }  // namespace sea

test/fixtures/sea/get-asset-keys.js

@@ -0,0 +1,9 @@
+'use strict';
+
+const { isSea, getAssetKeys } = require('node:sea');
+const assert = require('node:assert');
+
+assert(isSea());
+
+const keys = getAssetKeys();
+console.log('Asset keys:', JSON.stringify(keys.sort()));

test/parallel/test-sea-get-asset-keys.js

@@ -0,0 +1,11 @@
+'use strict';
+
+require('../common');
+
+const { getAssetKeys } = require('node:sea');
+const assert = require('node:assert');
+
+// Test that getAssetKeys throws when not in SEA
+assert.throws(() => getAssetKeys(), {
+  code: 'ERR_NOT_IN_SINGLE_EXECUTABLE_APPLICATION'
+});

test/sequential/sequential.status

@@ -57,6 +57,8 @@ test-watch-mode-inspect: SKIP
 test-single-executable-application: SKIP
 test-single-executable-application-assets: SKIP
 test-single-executable-application-assets-raw: SKIP
+test-single-executable-application-asset-keys-empty: SKIP
+test-single-executable-application-asset-keys: SKIP
 test-single-executable-application-disable-experimental-sea-warning: SKIP
 test-single-executable-application-empty: SKIP
 test-single-executable-application-exec-argv: SKIP

test/sequential/test-single-executable-application-asset-keys-empty.js

@@ -0,0 +1,65 @@
+'use strict';
+
+// This test verifies that the `getAssetKeys()` function works correctly
+// in a single executable application without any assets.
+
+require('../common');
+
+const {
+  generateSEA,
+  skipIfSingleExecutableIsNotSupported,
+} = require('../common/sea');
+
+skipIfSingleExecutableIsNotSupported();
+
+const tmpdir = require('../common/tmpdir');
+
+const { copyFileSync, writeFileSync, existsSync } = require('fs');
+const {
+  spawnSyncAndExitWithoutError,
+  spawnSyncAndAssert,
+} = require('../common/child_process');
+const assert = require('assert');
+const fixtures = require('../common/fixtures');
+
+const seaPrepBlob = tmpdir.resolve('sea-prep.blob');
+const outputFile = tmpdir.resolve(process.platform === 'win32' ? 'sea.exe' : 'sea');
+
+tmpdir.refresh();
+copyFileSync(fixtures.path('sea', 'get-asset-keys.js'), tmpdir.resolve('sea.js'));
+
+writeFileSync(tmpdir.resolve('sea-config.json'), `
+{
+  "main": "sea.js",
+  "output": "sea-prep.blob"
+}
+`, 'utf8');
+
+spawnSyncAndExitWithoutError(
+  process.execPath,
+  ['--experimental-sea-config', 'sea-config.json'],
+  {
+    env: {
+      NODE_DEBUG_NATIVE: 'SEA',
+      ...process.env,
+    },
+    cwd: tmpdir.path
+  },
+  {});
+
+assert(existsSync(seaPrepBlob));
+
+generateSEA(outputFile, process.execPath, seaPrepBlob);
+
+spawnSyncAndAssert(
+  outputFile,
+  {
+    env: {
+      ...process.env,
+      NODE_DEBUG_NATIVE: 'SEA',
+    }
+  },
+  {
+    stdout: /Asset keys: \[\]/,
+  }
+);

test/sequential/test-single-executable-application-asset-keys.js

@@ -0,0 +1,74 @@
+'use strict';
+
+// This test verifies that the `getAssetKeys()` function works correctly
+// in a single executable application with assets.
+
+require('../common');
+
+const {
+  generateSEA,
+  skipIfSingleExecutableIsNotSupported,
+} = require('../common/sea');
+
+skipIfSingleExecutableIsNotSupported();
+
+const tmpdir = require('../common/tmpdir');
+
+const { copyFileSync, writeFileSync, existsSync } = require('fs');
+const {
+  spawnSyncAndExitWithoutError,
+  spawnSyncAndAssert,
+} = require('../common/child_process');
+const assert = require('assert');
+const fixtures = require('../common/fixtures');
+
+const configFile = tmpdir.resolve('sea-config.json');
+const seaPrepBlob = tmpdir.resolve('sea-prep.blob');
+const outputFile = tmpdir.resolve(process.platform === 'win32' ? 'sea.exe' : 'sea');
+
+tmpdir.refresh();
+copyFileSync(fixtures.path('sea', 'get-asset-keys.js'), tmpdir.resolve('sea.js'));
+writeFileSync(tmpdir.resolve('asset-1.txt'), 'This is asset 1');
+writeFileSync(tmpdir.resolve('asset-2.txt'), 'This is asset 2');
+writeFileSync(tmpdir.resolve('asset-3.txt'), 'This is asset 3');
+
+writeFileSync(configFile, `
+{
+  "main": "sea.js",
+  "output": "sea-prep.blob",
+  "assets": {
+    "asset-1.txt": "asset-1.txt",
+    "asset-2.txt": "asset-2.txt",
+    "asset-3.txt": "asset-3.txt"
+  }
+}
+`, 'utf8');
+
+spawnSyncAndExitWithoutError(
+  process.execPath,
+  ['--experimental-sea-config', 'sea-config.json'],
+  {
+    env: {
+      NODE_DEBUG_NATIVE: 'SEA',
+      ...process.env,
+    },
+    cwd: tmpdir.path
+  },
+  {});
+
+assert(existsSync(seaPrepBlob));
+
+generateSEA(outputFile, process.execPath, seaPrepBlob);
+
+spawnSyncAndAssert(
+  outputFile,
+  {
+    env: {
+      ...process.env,
+      NODE_DEBUG_NATIVE: 'SEA',
+    }
+  },
+  {
+    stdout: /Asset keys: \["asset-1\.txt","asset-2\.txt","asset-3\.txt"\]/,
+  }
+);