Introduce `await Bun.file(path).exists()` (#3446)

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

4 files changed, 64 insertions, 0 deletions

diff --git a/src/bun.js/bindings/ZigGeneratedClasses.cpp b/src/bun.js/bindings/ZigGeneratedClasses.cpp
index 387580d54..b7461b5f0 100644
--- a/src/bun.js/bindings/ZigGeneratedClasses.cpp
+++ b/src/bun.js/bindings/ZigGeneratedClasses.cpp
@@ -103,6 +103,9 @@ extern "C" void BlobClass__finalize(void*);
 extern "C" EncodedJSValue BlobPrototype__getArrayBuffer(void* ptr, JSC::JSGlobalObject* lexicalGlobalObject, JSC::CallFrame* callFrame);
 JSC_DECLARE_HOST_FUNCTION(BlobPrototype__arrayBufferCallback);
 
+extern "C" EncodedJSValue BlobPrototype__getExists(void* ptr, JSC::JSGlobalObject* lexicalGlobalObject, JSC::CallFrame* callFrame);
+JSC_DECLARE_HOST_FUNCTION(BlobPrototype__existsCallback);
+
 extern "C" EncodedJSValue BlobPrototype__getFormData(void* ptr, JSC::JSGlobalObject* lexicalGlobalObject, JSC::CallFrame* callFrame);
 JSC_DECLARE_HOST_FUNCTION(BlobPrototype__formDataCallback);
 
@@ -137,6 +140,7 @@ STATIC_ASSERT_ISO_SUBSPACE_SHARABLE(JSBlobPrototype, JSBlobPrototype::Base);
 
 static const HashTableValue JSBlobPrototypeTableValues[] = {
     { "arrayBuffer"_s, static_cast<unsigned>(JSC::PropertyAttribute::Function | PropertyAttribute::DontDelete), NoIntrinsic, { HashTableValue::NativeFunctionType, BlobPrototype__arrayBufferCallback, 0 } },
+    { "exists"_s, static_cast<unsigned>(JSC::PropertyAttribute::Function | PropertyAttribute::DontDelete), NoIntrinsic, { HashTableValue::NativeFunctionType, BlobPrototype__existsCallback, 0 } },
     { "formData"_s, static_cast<unsigned>(JSC::PropertyAttribute::Function | PropertyAttribute::DontDelete), NoIntrinsic, { HashTableValue::NativeFunctionType, BlobPrototype__formDataCallback, 0 } },
     { "json"_s, static_cast<unsigned>(JSC::PropertyAttribute::Function | PropertyAttribute::DontDelete), NoIntrinsic, { HashTableValue::NativeFunctionType, BlobPrototype__jsonCallback, 0 } },
     { "lastModified"_s, static_cast<unsigned>(JSC::PropertyAttribute::ReadOnly | JSC::PropertyAttribute::CustomAccessor | JSC::PropertyAttribute::DOMAttribute | PropertyAttribute::DontDelete), NoIntrinsic, { HashTableValue::GetterSetterType, BlobPrototype__lastModifiedGetterWrap, 0 } },
@@ -190,6 +194,33 @@ JSC_DEFINE_HOST_FUNCTION(BlobPrototype__arrayBufferCallback, (JSGlobalObject * l
     return BlobPrototype__getArrayBuffer(thisObject->wrapped(), lexicalGlobalObject, callFrame);
 }
 
+JSC_DEFINE_HOST_FUNCTION(BlobPrototype__existsCallback, (JSGlobalObject * lexicalGlobalObject, CallFrame* callFrame))
+{
+    auto& vm = lexicalGlobalObject->vm();
+
+    JSBlob* thisObject = jsDynamicCast<JSBlob*>(callFrame->thisValue());
+
+    if (UNLIKELY(!thisObject)) {
+        auto throwScope = DECLARE_THROW_SCOPE(vm);
+        return throwVMTypeError(lexicalGlobalObject, throwScope);
+    }
+
+    JSC::EnsureStillAliveScope thisArg = JSC::EnsureStillAliveScope(thisObject);
+
+#ifdef BUN_DEBUG
+    /** View the file name of the JS file that called this function
+     * from a debugger */
+    SourceOrigin sourceOrigin = callFrame->callerSourceOrigin(vm);
+    const char* fileName = sourceOrigin.string().utf8().data();
+    static const char* lastFileName = nullptr;
+    if (lastFileName != fileName) {
+        lastFileName = fileName;
+    }
+#endif
+
+    return BlobPrototype__getExists(thisObject->wrapped(), lexicalGlobalObject, callFrame);
+}
+
 JSC_DEFINE_HOST_FUNCTION(BlobPrototype__formDataCallback, (JSGlobalObject * lexicalGlobalObject, CallFrame* callFrame))
 {
     auto& vm = lexicalGlobalObject->vm();
diff --git a/src/bun.js/bindings/generated_classes.zig b/src/bun.js/bindings/generated_classes.zig
index bdde69c1a..04a72d7ed 100644
--- a/src/bun.js/bindings/generated_classes.zig
+++ b/src/bun.js/bindings/generated_classes.zig
@@ -108,6 +108,8 @@ pub const JSBlob = struct {
 
         if (@TypeOf(Blob.getArrayBuffer) != CallbackType)
             @compileLog("Expected Blob.getArrayBuffer to be a callback but received " ++ @typeName(@TypeOf(Blob.getArrayBuffer)));
+        if (@TypeOf(Blob.getExists) != CallbackType)
+            @compileLog("Expected Blob.getExists to be a callback but received " ++ @typeName(@TypeOf(Blob.getExists)));
         if (@TypeOf(Blob.getFormData) != CallbackType)
             @compileLog("Expected Blob.getFormData to be a callback but received " ++ @typeName(@TypeOf(Blob.getFormData)));
         if (@TypeOf(Blob.getJSON) != CallbackType)
@@ -136,6 +138,7 @@ pub const JSBlob = struct {
             @export(Blob.constructor, .{ .name = "BlobClass__construct" });
             @export(Blob.finalize, .{ .name = "BlobClass__finalize" });
             @export(Blob.getArrayBuffer, .{ .name = "BlobPrototype__getArrayBuffer" });
+            @export(Blob.getExists, .{ .name = "BlobPrototype__getExists" });
             @export(Blob.getFormData, .{ .name = "BlobPrototype__getFormData" });
             @export(Blob.getJSON, .{ .name = "BlobPrototype__getJSON" });
             @export(Blob.getLastModified, .{ .name = "BlobPrototype__getLastModified" });
diff --git a/src/bun.js/webcore/blob.zig b/src/bun.js/webcore/blob.zig
index 868acbb80..faf503a3f 100644
--- a/src/bun.js/webcore/blob.zig
+++ b/src/bun.js/webcore/blob.zig
@@ -319,6 +319,7 @@ pub const Blob = struct {
             },
         );
     }
+
     pub fn writeFormat(this: *const Blob, comptime Formatter: type, formatter: *Formatter, writer: anytype, comptime enable_ansi_colors: bool) !void {
         const Writer = @TypeOf(writer);
 
@@ -2324,6 +2325,34 @@ pub const Blob = struct {
         return promisified(this.toFormData(globalThis, .temporary), globalThis);
     }
 
+    fn getExistsSync(this: *Blob) JSC.JSValue {
+        if (this.size == Blob.max_size) {
+            this.resolveSize();
+        }
+
+        // If there's no store that means it's empty and we just return true
+        // it will not error to return an empty Blob
+        var store = this.store orelse return JSValue.jsBoolean(true);
+
+        if (store.data == .bytes) {
+            // Bytes will never error
+            return JSValue.jsBoolean(true);
+        }
+
+        // We say regular files and pipes exist.
+        // This is mostly meant for "Can we use this in new Response(file)?"
+        return JSValue.jsBoolean(std.os.S.ISREG(store.data.file.mode) or std.os.S.ISFIFO(store.data.file.mode));
+    }
+
+    // This mostly means 'can it be read?'
+    pub fn getExists(
+        this: *Blob,
+        globalThis: *JSC.JSGlobalObject,
+        _: *JSC.CallFrame,
+    ) callconv(.C) JSValue {
+        return JSC.JSPromise.resolvedPromiseValue(globalThis, this.getExistsSync());
+    }
+
     pub fn getWriter(
         this: *Blob,
         globalThis: *JSC.JSGlobalObject,
diff --git a/src/bun.js/webcore/response.classes.ts b/src/bun.js/webcore/response.classes.ts
index b6ad452d2..c11cb10b2 100644
--- a/src/bun.js/webcore/response.classes.ts
+++ b/src/bun.js/webcore/response.classes.ts
@@ -132,6 +132,7 @@ export default [
       slice: { fn: "getSlice", length: 2 },
       stream: { fn: "getStream", length: 1 },
       formData: { fn: "getFormData" },
+      exists: { fn: "getExists", length: 0 },
 
       type: {
         getter: "getType",