node-api: add node_api_symbol_for()

doc/api/n-api.md

@@ -2492,6 +2492,38 @@ This API creates a JavaScript `symbol` value from a UTF8-encoded C string.
 The JavaScript `symbol` type is described in [Section 19.4][]
 of the ECMAScript Language Specification.
 
+#### `node_api_symbol_for`
+
+<!-- YAML
+added: REPLACEME
+napiVersion: REPLACEME
+-->
+
+> Stability: 1 - Experimental
+
+```c
+napi_status node_api_symbol_for(napi_env env,
+                                const char* utf8description,
+                                size_t length,
+                                napi_value* result)
+```
+
+* `[in] env`: The environment that the API is invoked under.
+* `[in] utf8description`: UTF-8 C string representing the text to be used as the
+  description for the symbol.
+* `[in] length`: The length of the description string in bytes, or
+  `NAPI_AUTO_LENGTH` if it is null-terminated.
+* `[out] result`: A `napi_value` representing a JavaScript `symbol`.
+
+Returns `napi_ok` if the API succeeded.
+
+This API searches in the global registry for an existing symbol with the given
+description. If the symbol already exists it will be returned, otherwise a new
+symbol will be created in the registry.
+
+The JavaScript `symbol` type is described in [Section 19.4][] of the ECMAScript
+Language Specification.
+
 #### `napi_create_typedarray`
 
 <!-- YAML

src/js_native_api.h

@@ -93,6 +93,12 @@ NAPI_EXTERN napi_status napi_create_string_utf16(napi_env env,
 NAPI_EXTERN napi_status napi_create_symbol(napi_env env,
                                            napi_value description,
                                            napi_value* result);
+#ifdef NAPI_EXPERIMENTAL
+NAPI_EXTERN napi_status node_api_symbol_for(napi_env env,
+                                            const char* utf8description,
+                                            size_t length,
+                                            napi_value* result);
+#endif  // NAPI_EXPERIMENTAL
 NAPI_EXTERN napi_status napi_create_function(napi_env env,
                                              const char* utf8name,
                                              size_t length,

src/js_native_api_v8.cc

@@ -1662,6 +1662,27 @@ napi_status napi_create_symbol(napi_env env,
   return napi_clear_last_error(env);
 }
 
+napi_status node_api_symbol_for(napi_env env,
+                                const char* utf8description,
+                                size_t length,
+                                napi_value* result) {
+  CHECK_ENV(env);
+  CHECK_ARG(env, result);
+
+  napi_value js_description_string;
+  STATUS_CALL(napi_create_string_utf8(env,
+                                      utf8description,
+                                      length,
+                                      &js_description_string));
+  v8::Local<v8::String> description_string =
+    v8impl::V8LocalValueFromJsValue(js_description_string).As<v8::String>();
+
+  *result = v8impl::JsValueFromV8LocalValue(
+    v8::Symbol::For(env->isolate, description_string));
+
+  return napi_clear_last_error(env);
+}
+
 static inline napi_status set_error_code(napi_env env,
                                          v8::Local<v8::Value> error,
                                          napi_value code,

test/js-native-api/test_properties/test.js

@@ -35,12 +35,11 @@ assert.ok(!propertyNames.includes('readwriteAccessor2'));
 assert.ok(!propertyNames.includes('readonlyAccessor1'));
 assert.ok(!propertyNames.includes('readonlyAccessor2'));
 
-// Validate property created with symbol
-const start = 'Symbol('.length;
-const end = start + 'NameKeySymbol'.length;
-const symbolDescription =
-    String(Object.getOwnPropertySymbols(test_object)[0]).slice(start, end);
-assert.strictEqual(symbolDescription, 'NameKeySymbol');
+// Validate properties created with symbol
+const propertySymbols = Object.getOwnPropertySymbols(test_object);
+assert.strictEqual(propertySymbols[0].toString(), 'Symbol(NameKeySymbol)');
+assert.strictEqual(propertySymbols[1].toString(), 'Symbol()');
+assert.strictEqual(propertySymbols[2], Symbol.for('NameKeySymbolFor'));
 
 // The napi_writable attribute should be ignored for accessors.
 const readwriteAccessor1Descriptor =

test/js-native-api/test_properties/test_properties.c

@@ -1,3 +1,4 @@
+#define NAPI_EXPERIMENTAL
 #include <js_native_api.h>
 #include "../common.h"
 
@@ -77,13 +78,25 @@ napi_value Init(napi_env env, napi_value exports) {
   NODE_API_CALL(env,
       napi_create_symbol(env, symbol_description, &name_symbol));
 
+  napi_value name_symbol_descriptionless;
+  NODE_API_CALL(env,
+      napi_create_symbol(env, NULL, &name_symbol_descriptionless));
+
+  napi_value name_symbol_for;
+  NODE_API_CALL(env, node_api_symbol_for(env,
+                                         "NameKeySymbolFor",
+                                         NAPI_AUTO_LENGTH,
+                                         &name_symbol_for));
+
   napi_property_descriptor properties[] = {
     { "echo", 0, Echo, 0, 0, 0, napi_enumerable, 0 },
     { "readwriteValue", 0, 0, 0, 0, number, napi_enumerable | napi_writable, 0 },
     { "readonlyValue", 0, 0, 0, 0, number, napi_enumerable, 0},
     { "hiddenValue", 0, 0, 0, 0, number, napi_default, 0},
     { NULL, name_value, 0, 0, 0, number, napi_enumerable, 0},
     { NULL, name_symbol, 0, 0, 0, number, napi_enumerable, 0},
+    { NULL, name_symbol_descriptionless, 0, 0, 0, number, napi_enumerable, 0},
+    { NULL, name_symbol_for, 0, 0, 0, number, napi_enumerable, 0},
     { "readwriteAccessor1", 0, 0, GetValue, SetValue, 0, napi_default, 0},
     { "readwriteAccessor2", 0, 0, GetValue, SetValue, 0, napi_writable, 0},
     { "readonlyAccessor1", 0, 0, GetValue, NULL, 0, napi_default, 0},

test/js-native-api/test_reference/test.js

@@ -21,6 +21,25 @@ async function runTests() {
   })();
   test_reference.deleteReference();
 
+  (() => {
+    const symbol = test_reference.createSymbolFor('testSymFor');
+    test_reference.createReference(symbol, 0);
+    assert.strictEqual(test_reference.referenceValue, symbol);
+    assert.strictEqual(test_reference.referenceValue, Symbol.for('testSymFor'));
+  })();
+  test_reference.deleteReference();
+
+  (() => {
+    const symbol = test_reference.createSymbolForEmptyString();
+    test_reference.createReference(symbol, 0);
+    assert.strictEqual(test_reference.referenceValue, symbol);
+    assert.strictEqual(test_reference.referenceValue, Symbol.for(''));
+  })();
+  test_reference.deleteReference();
+
+  assert.throws(() => test_reference.createSymbolForIncorrectLength(),
+                /Invalid argument/);
+
   (() => {
     const value = test_reference.createExternal();
     assert.strictEqual(test_reference.finalizeCount, 0);

test/js-native-api/test_reference/test_reference.c

@@ -1,3 +1,4 @@
+#define NAPI_EXPERIMENTAL
 #include <stdlib.h>
 #include <assert.h>
 #include <js_native_api.h>
@@ -49,6 +50,41 @@ static napi_value CreateSymbol(napi_env env, napi_callback_info info) {
     return result_symbol;
 }
 
+static napi_value CreateSymbolFor(napi_env env, napi_callback_info info) {
+
+    size_t argc = 1;
+    napi_value args[1];
+
+    char description[256];
+    size_t description_length;
+
+    NODE_API_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL,NULL));
+    NODE_API_ASSERT(env, argc == 1, "Expect one argument only (symbol description)");
+
+    NODE_API_CALL(env, napi_get_value_string_utf8(env, args[0], description, sizeof(description), &description_length));
+    NODE_API_ASSERT(env, description_length <= 255, "Cannot accommodate descriptions longer than 255 bytes");
+
+    napi_value result_symbol;
+
+    NODE_API_CALL(env, node_api_symbol_for(env,
+                                           description,
+                                           description_length,
+                                           &result_symbol));
+    return result_symbol;
+}
+
+static napi_value CreateSymbolForEmptyString(napi_env env, napi_callback_info info) {
+  napi_value result_symbol;
+  NODE_API_CALL(env, node_api_symbol_for(env, NULL, 0, &result_symbol));
+  return result_symbol;
+}
+
+static napi_value CreateSymbolForIncorrectLength(napi_env env, napi_callback_info info) {
+  napi_value result_symbol;
+  NODE_API_CALL(env, node_api_symbol_for(env, NULL, 5, &result_symbol));
+  return result_symbol;
+}
+
 static napi_value
 CreateExternalWithFinalize(napi_env env, napi_callback_info info) {
   napi_value result;
@@ -190,6 +226,9 @@ napi_value Init(napi_env env, napi_value exports) {
     DECLARE_NODE_API_PROPERTY("checkExternal", CheckExternal),
     DECLARE_NODE_API_PROPERTY("createReference", CreateReference),
     DECLARE_NODE_API_PROPERTY("createSymbol", CreateSymbol),
+    DECLARE_NODE_API_PROPERTY("createSymbolFor", CreateSymbolFor),
+    DECLARE_NODE_API_PROPERTY("createSymbolForEmptyString", CreateSymbolForEmptyString),
+    DECLARE_NODE_API_PROPERTY("createSymbolForIncorrectLength", CreateSymbolForIncorrectLength),
     DECLARE_NODE_API_PROPERTY("deleteReference", DeleteReference),
     DECLARE_NODE_API_PROPERTY("incrementRefcount", IncrementRefcount),
     DECLARE_NODE_API_PROPERTY("decrementRefcount", DecrementRefcount),