fs: throw errors on invalid paths synchronously

- Throw getPathFromURL() and nullCheck() errors synchronously instead
  of deferring them to the next tick, since we already throw
  validatePath() errors synchronously.
- Merge nullCheck() into validatePath()
- Never throws in `fs.exists()`, instead, invoke the callback with
  false, or emit a warning when the callback is not a function.
  This is to bring it inline with fs.existsSync(), which never throws.
- Updates the comment of rethrow()
- Throw ERR_INVALID_ARG_VALUE for null checks

PR-URL: https://github.com/nodejs/node/pull/18308
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 14 insertions, 11 deletions

diff --git a/test/parallel/test-fs-exists.js b/test/parallel/test-fs-exists.js
index a526373c6a..c52679764b 100644
--- a/test/parallel/test-fs-exists.js
+++ b/test/parallel/test-fs-exists.js
@@ -26,30 +26,33 @@ const fs = require('fs');
 const { URL } = require('url');
 const f = __filename;
 
+// Only warnings are emitted when the callback is invalid
+assert.doesNotThrow(() => fs.exists(f));
+assert.doesNotThrow(() => fs.exists());
+assert.doesNotThrow(() => fs.exists(f, {}));
+
 fs.exists(f, common.mustCall(function(y) {
   assert.strictEqual(y, true);
 }));
 
-assert.doesNotThrow(() => fs.exists(f));
-
 fs.exists(`${f}-NO`, common.mustCall(function(y) {
   assert.strictEqual(y, false);
 }));
 
+// If the path is invalid, fs.exists will still invoke the callback with false
+// instead of throwing errors
 fs.exists(new URL('https://foo'), common.mustCall(function(y) {
   assert.strictEqual(y, false);
 }));
 
+fs.exists({}, common.mustCall(function(y) {
+  assert.strictEqual(y, false);
+}));
+
 assert(fs.existsSync(f));
 assert(!fs.existsSync(`${f}-NO`));
 
-common.expectsError(
-  () => { fs.exists(() => {}); },
-  {
-    code: 'ERR_INVALID_ARG_TYPE',
-    message: 'The "path" argument must be one of type string, Buffer, or URL',
-    type: TypeError
-  }
-);
-
+// fs.existsSync() never throws
 assert(!fs.existsSync());
+assert(!fs.existsSync({}));
+assert(!fs.existsSync(new URL('https://foo')));