Implement `import.meta.main` (#2556)

* Implement `import.meta.main`

* Update main-test-1.js

* Update fs.test.ts

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

10 files changed, 89 insertions, 8 deletions

diff --git a/packages/bun-types/globals.d.ts b/packages/bun-types/globals.d.ts
index 6ff2e9970..a9fdc01a1 100644
--- a/packages/bun-types/globals.d.ts
+++ b/packages/bun-types/globals.d.ts
@@ -234,21 +234,21 @@ interface ImportMeta {
    * "file:///Users/me/projects/my-app/src/my-app.ts"
    * ```
    */
-  url: string;
+  readonly url: string;
   /**
    * Absolute path to the source file
    */
-  path: string;
+  readonly path: string;
   /**
    * Absolute path to the directory containing the source file.
    *
    * Does not have a trailing slash
    */
-  dir: string;
+  readonly dir: string;
   /**
    * Filename of the source file
    */
-  file: string;
+  readonly file: string;
   /**
    * Resolve a module ID the same as if you imported it
    *
@@ -284,6 +284,25 @@ interface ImportMeta {
    * relevant.
    */
   require: NodeJS.Require;
+
+  /**
+   * Did the current file start the process?
+   *
+   * @example
+   * ```ts
+   * if (import.meta.main) {
+   *  console.log("I started the process!");
+   * }
+   * ```
+   *
+   * @example
+   * ```ts
+   * console.log(
+   *   import.meta.main === (import.meta.path === Bun.main)
+   * )
+   * ```
+   */
+  readonly main: boolean;
 }
 
 /**
diff --git a/src/bun.js/bindings/ImportMetaObject.cpp b/src/bun.js/bindings/ImportMetaObject.cpp
index f8b6d0f9b..7831cf881 100644
--- a/src/bun.js/bindings/ImportMetaObject.cpp
+++ b/src/bun.js/bindings/ImportMetaObject.cpp
@@ -39,6 +39,7 @@
 
 #include "JSDOMURL.h"
 #include "JavaScriptCore/JSNativeStdFunction.h"
+#include "JavaScriptCore/GetterSetter.h"
 
 namespace Zig {
 using namespace JSC;
@@ -84,7 +85,7 @@ static EncodedJSValue functionRequireResolve(JSC::JSGlobalObject* globalObject,
             // require.resolve also supports a paths array
             // we only support a single path
             if (!fromValue.isUndefinedOrNull() && fromValue.isObject()) {
-                 if (JSValue pathsValue = fromValue.getObject()->getIfPropertyExists(globalObject, JSC::Identifier::fromString(vm, "paths"_s))) {
+                if (JSValue pathsValue = fromValue.getObject()->getIfPropertyExists(globalObject, JSC::Identifier::fromString(vm, "paths"_s))) {
                     if (JSC::JSArray* array = JSC::jsDynamicCast<JSC::JSArray*>(pathsValue)) {
                         if (array->length() > 0) {
                             fromValue = array->getIndex(globalObject, 0);
@@ -413,7 +414,13 @@ void ImportMetaObjectPrototype::finishCreation(VM& vm, JSGlobalObject* globalObj
     this->putDirect(vm, builtinNames.dirPublicName(), jsEmptyString(vm), 0);
     this->putDirect(vm, builtinNames.pathPublicName(), jsEmptyString(vm), 0);
     this->putDirect(vm, builtinNames.urlPublicName(), jsEmptyString(vm), 0);
-    this->putDirect(vm, builtinNames.mainPublicName(), jsBoolean(false), 0);
+
+    this->putDirect(
+        vm,
+        builtinNames.mainPublicName(),
+        GetterSetter::create(vm, globalObject, JSFunction::create(vm, importMetaObjectMainCodeGenerator(vm), globalObject), nullptr),
+        JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::Accessor | JSC::PropertyAttribute::Builtin | 0);
+        
     this->putDirect(vm, Identifier::fromString(vm, "primordials"_s), jsUndefined(), JSC::PropertyAttribute::DontEnum | 0);
 
     String requireString = "[[require]]"_s;
diff --git a/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.cpp b/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.cpp
index d014618c3..a9ce25b04 100644
--- a/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.cpp
+++ b/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.cpp
@@ -255,6 +255,17 @@ const char* const s_importMetaObjectRequireCode =
     "})\n" \
 ;
 
+const JSC::ConstructAbility s_importMetaObjectMainCodeConstructAbility = JSC::ConstructAbility::CannotConstruct;
+const JSC::ConstructorKind s_importMetaObjectMainCodeConstructorKind = JSC::ConstructorKind::None;
+const JSC::ImplementationVisibility s_importMetaObjectMainCodeImplementationVisibility = JSC::ImplementationVisibility::Public;
+const int s_importMetaObjectMainCodeLength = 52;
+static const JSC::Intrinsic s_importMetaObjectMainCodeIntrinsic = JSC::NoIntrinsic;
+const char* const s_importMetaObjectMainCode =
+    "(function () {\n" \
+    "  return this.path === @Bun.main;\n" \
+    "})\n" \
+;
+
 
 #define DEFINE_BUILTIN_GENERATOR(codeName, functionName, overriddenName, argumentCount) \
 JSC::FunctionExecutable* codeName##Generator(JSC::VM& vm) \
diff --git a/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.h b/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.h
index d47c86980..1a7c5d844 100644
--- a/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.h
+++ b/src/bun.js/builtins/cpp/ImportMetaObjectBuiltins.h
@@ -67,27 +67,36 @@ extern const int s_importMetaObjectRequireCodeLength;
 extern const JSC::ConstructAbility s_importMetaObjectRequireCodeConstructAbility;
 extern const JSC::ConstructorKind s_importMetaObjectRequireCodeConstructorKind;
 extern const JSC::ImplementationVisibility s_importMetaObjectRequireCodeImplementationVisibility;
+extern const char* const s_importMetaObjectMainCode;
+extern const int s_importMetaObjectMainCodeLength;
+extern const JSC::ConstructAbility s_importMetaObjectMainCodeConstructAbility;
+extern const JSC::ConstructorKind s_importMetaObjectMainCodeConstructorKind;
+extern const JSC::ImplementationVisibility s_importMetaObjectMainCodeImplementationVisibility;
 
 #define WEBCORE_FOREACH_IMPORTMETAOBJECT_BUILTIN_DATA(macro) \
     macro(loadCJS2ESM, importMetaObjectLoadCJS2ESM, 1) \
     macro(requireESM, importMetaObjectRequireESM, 1) \
     macro(internalRequire, importMetaObjectInternalRequire, 1) \
     macro(require, importMetaObjectRequire, 1) \
+    macro(main, importMetaObjectMain, 0) \
 
 #define WEBCORE_BUILTIN_IMPORTMETAOBJECT_LOADCJS2ESM 1
 #define WEBCORE_BUILTIN_IMPORTMETAOBJECT_REQUIREESM 1
 #define WEBCORE_BUILTIN_IMPORTMETAOBJECT_INTERNALREQUIRE 1
 #define WEBCORE_BUILTIN_IMPORTMETAOBJECT_REQUIRE 1
+#define WEBCORE_BUILTIN_IMPORTMETAOBJECT_MAIN 1
 
 #define WEBCORE_FOREACH_IMPORTMETAOBJECT_BUILTIN_CODE(macro) \
     macro(importMetaObjectLoadCJS2ESMCode, loadCJS2ESM, ASCIILiteral(), s_importMetaObjectLoadCJS2ESMCodeLength) \
     macro(importMetaObjectRequireESMCode, requireESM, ASCIILiteral(), s_importMetaObjectRequireESMCodeLength) \
     macro(importMetaObjectInternalRequireCode, internalRequire, ASCIILiteral(), s_importMetaObjectInternalRequireCodeLength) \
     macro(importMetaObjectRequireCode, require, ASCIILiteral(), s_importMetaObjectRequireCodeLength) \
+    macro(importMetaObjectMainCode, main, "get main"_s, s_importMetaObjectMainCodeLength) \
 
 #define WEBCORE_FOREACH_IMPORTMETAOBJECT_BUILTIN_FUNCTION_NAME(macro) \
     macro(internalRequire) \
     macro(loadCJS2ESM) \
+    macro(main) \
     macro(require) \
     macro(requireESM) \
 
diff --git a/src/bun.js/builtins/cpp/ProcessObjectInternalsBuiltins.cpp b/src/bun.js/builtins/cpp/ProcessObjectInternalsBuiltins.cpp
index c2276138e..bd496deff 100644
--- a/src/bun.js/builtins/cpp/ProcessObjectInternalsBuiltins.cpp
+++ b/src/bun.js/builtins/cpp/ProcessObjectInternalsBuiltins.cpp
@@ -51,7 +51,7 @@ namespace WebCore {
 const JSC::ConstructAbility s_processObjectInternalsBindingCodeConstructAbility = JSC::ConstructAbility::CannotConstruct;
 const JSC::ConstructorKind s_processObjectInternalsBindingCodeConstructorKind = JSC::ConstructorKind::None;
 const JSC::ImplementationVisibility s_processObjectInternalsBindingCodeImplementationVisibility = JSC::ImplementationVisibility::Public;
-const int s_processObjectInternalsBindingCodeLength = 688;
+const int s_processObjectInternalsBindingCodeLength = 709;
 static const JSC::Intrinsic s_processObjectInternalsBindingCodeIntrinsic = JSC::NoIntrinsic;
 const char* const s_processObjectInternalsBindingCode =
     "(function (bindingName) {\n" \
@@ -64,6 +64,9 @@ const char* const s_processObjectInternalsBindingCode =
     "  var cache = globalThis.Symbol.for(\"process.bindings.constants\");\n" \
     "  var constants = globalThis[cache];\n" \
     "  if (!constants) {\n" \
+    "    //\n" \
+    "    //\n" \
+    "    //\n" \
     "    const {constants: fs} = globalThis[globalThis.Symbol.for(\"Bun.lazy\")](\n" \
     "      \"createImportMeta\",\n" \
     "      \"node:process\"\n" \
diff --git a/src/bun.js/builtins/js/ImportMetaObject.js b/src/bun.js/builtins/js/ImportMetaObject.js
index 82701554d..b8d7900c0 100644
--- a/src/bun.js/builtins/js/ImportMetaObject.js
+++ b/src/bun.js/builtins/js/ImportMetaObject.js
@@ -202,4 +202,9 @@ function require(name) {
   }
 
   return @internalRequire(@resolveSync(name, from));
-}
\ No newline at end of file
+}
+
+@getter
+function main() {
+  return this.path === @Bun.main;
+}
diff --git a/test/js/bun/resolve/import-meta.test.js b/test/js/bun/resolve/import-meta.test.js
index a95b1a0ea..c4bbdb1a6 100644
--- a/test/js/bun/resolve/import-meta.test.js
+++ b/test/js/bun/resolve/import-meta.test.js
@@ -2,6 +2,9 @@ import { it, expect } from "bun:test";
 import { mkdirSync, rmSync, writeFileSync } from "node:fs";
 import * as Module from "node:module";
 import sync from "./require-json.json";
+import { spawnSync } from "bun";
+import { bunEnv, bunExe } from "harness";
+import { join } from "node:path";
 
 const { path, dir } = import.meta;
 
@@ -9,6 +12,17 @@ it("primordials are not here!", () => {
   expect(import.meta.primordials === undefined).toBe(true);
 });
 
+it("import.meta.main", () => {
+  const { exitCode } = spawnSync({
+    cmd: [bunExe(), "run", join(import.meta.dir, "./main-test-script.js")],
+    env: bunEnv,
+    stderr: "inherit",
+    stdout: "inherit",
+    stdin: null,
+  });
+  expect(exitCode).toBe(0);
+});
+
 it("import.meta.resolveSync", () => {
   expect(import.meta.resolveSync("./" + import.meta.file, import.meta.path)).toBe(path);
   const require = Module.createRequire(import.meta.path);
diff --git a/test/js/bun/resolve/main-test-1.js b/test/js/bun/resolve/main-test-1.js
new file mode 100644
index 000000000..8e83d65e1
--- /dev/null
+++ b/test/js/bun/resolve/main-test-1.js
@@ -0,0 +1,5 @@
+if (import.meta.main) {
+  process.exit(1);
+}
+
+export const pass = true;
diff --git a/test/js/bun/resolve/main-test-script.js b/test/js/bun/resolve/main-test-script.js
new file mode 100644
index 000000000..d5b0cb67a
--- /dev/null
+++ b/test/js/bun/resolve/main-test-script.js
@@ -0,0 +1,7 @@
+import "./main-test-1";
+
+if (!import.meta.main) {
+  process.exit(1);
+}
+
+process.exit(0);
diff --git a/test/js/node/fs/fs.test.ts b/test/js/node/fs/fs.test.ts
index fa27ab246..f7b343539 100644
--- a/test/js/node/fs/fs.test.ts
+++ b/test/js/node/fs/fs.test.ts
@@ -38,6 +38,7 @@ import { ReadStream as ReadStreamStar_, WriteStream as WriteStreamStar_ } from "
 const Buffer = globalThis.Buffer || Uint8Array;
 
 if (!import.meta.dir) {
+  //@ts-expect-error
   import.meta.dir = ".";
 }