n-api: remove napi_get_value_string_length()

This API doesn't serve much purpose, and is only likely to cause
confusion and bugs. The intention was that this would return the
number of characters in a string independent of encoding, but
that's not generally useful. In almost all cases, one of the
encoding-specific napi_get_value_string_* APIs is more correct.
(Pass a null buffer if only the encoded length is desired.)

Anyway the current implementation of napi_get_value_string_length()
is technically wrong: it returns the number of 2-byte code units of
the UTF-16 encoding, but there are actually some characters that
are encoded as two UTF-16 code units.

Note the JavaScript String.prototype.length property returns the
number of UTF-16 code units, which may be different from the number
of characters. So, getting the true character count is not common
with JavaScript, and is probably best left to specialized
internationalization libraries.

PR-URL: #12496
Fixes: nodejs/abi-stable-node#226
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/node_api.cc

@@ -1719,21 +1719,6 @@ napi_status napi_get_value_bool(napi_env env, napi_value value, bool* result) {
   return napi_ok;
 }
 
-// Gets the number of CHARACTERS in the string.
-napi_status napi_get_value_string_length(napi_env env,
-                                         napi_value value,
-                                         size_t* result) {
-  NAPI_PREAMBLE(env);
-  CHECK_ARG(env, result);
-
-  v8::Local<v8::Value> val = v8impl::V8LocalValueFromJsValue(value);
-  RETURN_STATUS_IF_FALSE(env, val->IsString(), napi_string_expected);
-
-  *result = val.As<v8::String>()->Length();
-
-  return GET_RETURN_STATUS(env);
-}
-
 // Copies a JavaScript string into a LATIN-1 string buffer. The result is the
 // number of bytes (excluding the null terminator) copied into buf.
 // A sufficient buffer size should be greater than the length of string,

src/node_api.h

@@ -171,11 +171,6 @@ NAPI_EXTERN napi_status napi_get_value_bool(napi_env env,
                                             napi_value value,
                                             bool* result);
 
-// Gets the number of CHARACTERS in the string.
-NAPI_EXTERN napi_status napi_get_value_string_length(napi_env env,
-                                                     napi_value value,
-                                                     size_t* result);
-
 // Copies LATIN-1 encoded bytes from a string into a buffer.
 NAPI_EXTERN napi_status napi_get_value_string_latin1(napi_env env,
                                                      napi_value value,

test/addons-napi/test_string/test.js

@@ -9,7 +9,7 @@ const empty = '';
 assert.strictEqual(test_string.TestLatin1(empty), empty);
 assert.strictEqual(test_string.TestUtf8(empty), empty);
 assert.strictEqual(test_string.TestUtf16(empty), empty);
-assert.strictEqual(test_string.Length(empty), 0);
+assert.strictEqual(test_string.Utf16Length(empty), 0);
 assert.strictEqual(test_string.Utf8Length(empty), 0);
 
 const str1 = 'hello world';
@@ -19,7 +19,7 @@ assert.strictEqual(test_string.TestUtf16(str1), str1);
 assert.strictEqual(test_string.TestLatin1Insufficient(str1), str1.slice(0, 3));
 assert.strictEqual(test_string.TestUtf8Insufficient(str1), str1.slice(0, 3));
 assert.strictEqual(test_string.TestUtf16Insufficient(str1), str1.slice(0, 3));
-assert.strictEqual(test_string.Length(str1), 11);
+assert.strictEqual(test_string.Utf16Length(str1), 11);
 assert.strictEqual(test_string.Utf8Length(str1), 11);
 
 const str2 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
@@ -29,7 +29,7 @@ assert.strictEqual(test_string.TestUtf16(str2), str2);
 assert.strictEqual(test_string.TestLatin1Insufficient(str2), str2.slice(0, 3));
 assert.strictEqual(test_string.TestUtf8Insufficient(str2), str2.slice(0, 3));
 assert.strictEqual(test_string.TestUtf16Insufficient(str2), str2.slice(0, 3));
-assert.strictEqual(test_string.Length(str2), 62);
+assert.strictEqual(test_string.Utf16Length(str2), 62);
 assert.strictEqual(test_string.Utf8Length(str2), 62);
 
 const str3 = '?!@#$%^&*()_+-=[]{}/.,<>\'"\\';
@@ -39,7 +39,7 @@ assert.strictEqual(test_string.TestUtf16(str3), str3);
 assert.strictEqual(test_string.TestLatin1Insufficient(str3), str3.slice(0, 3));
 assert.strictEqual(test_string.TestUtf8Insufficient(str3), str3.slice(0, 3));
 assert.strictEqual(test_string.TestUtf16Insufficient(str3), str3.slice(0, 3));
-assert.strictEqual(test_string.Length(str3), 27);
+assert.strictEqual(test_string.Utf16Length(str3), 27);
 assert.strictEqual(test_string.Utf8Length(str3), 27);
 
 const str4 = '¡¢£¤¥¦§¨©ª«¬­®¯°±²³´µ¶·¸¹º»¼½¾¿';
@@ -49,7 +49,7 @@ assert.strictEqual(test_string.TestUtf16(str4), str4);
 assert.strictEqual(test_string.TestLatin1Insufficient(str4), str4.slice(0, 3));
 assert.strictEqual(test_string.TestUtf8Insufficient(str4), str4.slice(0, 1));
 assert.strictEqual(test_string.TestUtf16Insufficient(str4), str4.slice(0, 3));
-assert.strictEqual(test_string.Length(str4), 31);
+assert.strictEqual(test_string.Utf16Length(str4), 31);
 assert.strictEqual(test_string.Utf8Length(str4), 62);
 
 const str5 = 'ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþ';
@@ -59,13 +59,13 @@ assert.strictEqual(test_string.TestUtf16(str5), str5);
 assert.strictEqual(test_string.TestLatin1Insufficient(str5), str5.slice(0, 3));
 assert.strictEqual(test_string.TestUtf8Insufficient(str5), str5.slice(0, 1));
 assert.strictEqual(test_string.TestUtf16Insufficient(str5), str5.slice(0, 3));
-assert.strictEqual(test_string.Length(str5), 63);
+assert.strictEqual(test_string.Utf16Length(str5), 63);
 assert.strictEqual(test_string.Utf8Length(str5), 126);
 
 const str6 = '\u{2003}\u{2101}\u{2001}\u{202}\u{2011}';
 assert.strictEqual(test_string.TestUtf8(str6), str6);
 assert.strictEqual(test_string.TestUtf16(str6), str6);
 assert.strictEqual(test_string.TestUtf8Insufficient(str6), str6.slice(0, 1));
 assert.strictEqual(test_string.TestUtf16Insufficient(str6), str6.slice(0, 3));
-assert.strictEqual(test_string.Length(str6), 5);
+assert.strictEqual(test_string.Utf16Length(str6), 5);
 assert.strictEqual(test_string.Utf8Length(str6), 14);

test/addons-napi/test_string/test_string.c

@@ -157,7 +157,7 @@ napi_value TestUtf16Insufficient(napi_env env, napi_callback_info info) {
   return output;
 }
 
-napi_value Length(napi_env env, napi_callback_info info) {
+napi_value Utf16Length(napi_env env, napi_callback_info info) {
   size_t argc = 1;
   napi_value args[1];
   NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));
@@ -171,7 +171,7 @@ napi_value Length(napi_env env, napi_callback_info info) {
     "Wrong type of argment. Expects a string.");
 
   size_t length;
-  NAPI_CALL(env, napi_get_value_string_length(env, args[0], &length));
+  NAPI_CALL(env, napi_get_value_string_utf16(env, args[0], NULL, 0, &length));
 
   napi_value output;
   NAPI_CALL(env, napi_create_number(env, (double)length, &output));
@@ -209,7 +209,7 @@ void Init(napi_env env, napi_value exports, napi_value module, void* priv) {
     DECLARE_NAPI_PROPERTY("TestUtf8Insufficient", TestUtf8Insufficient),
     DECLARE_NAPI_PROPERTY("TestUtf16", TestUtf16),
     DECLARE_NAPI_PROPERTY("TestUtf16Insufficient", TestUtf16Insufficient),
-    DECLARE_NAPI_PROPERTY("Length", Length),
+    DECLARE_NAPI_PROPERTY("Utf16Length", Utf16Length),
     DECLARE_NAPI_PROPERTY("Utf8Length", Utf8Length),
   };