test: add test for Module._stat

Module._stat landed in #44537 without
a test, so this change adds one.
Signed-off-by: Darshan Sen <raisinten@gmail.com>
PR-URL: #44713
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>

Author: RaisinTen

test/parallel/test-module-stat.js

@@ -0,0 +1,25 @@
+'use strict';
+require('../common');
+
+// This tests Module._stat.
+
+constModule=require('module');
+constfs=require('fs');
+consttmpdir=require('../common/tmpdir');
+const{ ok, strictEqual }=require('assert');
+const{ join }=require('path');
+
+constdirectory=join(tmpdir.path,'directory');
+constdoesNotExist=join(tmpdir.path,'does-not-exist');
+constfile=join(tmpdir.path,'file.js');
+
+tmpdir.refresh();
+fs.writeFileSync(file,"module.exports = { a: 'b' }");
+fs.mkdirSync(directory);
+
+strictEqual(Module._stat(directory),1);// Returns 1 for directories.
+strictEqual(Module._stat(file),0);// Returns 0 for files.
+ok(Module._stat(doesNotExist)<0);// Returns a negative integer for any other kind of strings.
+
+// TODO(RaisinTen): Add tests that make sure that Module._stat() does not crash when called
+// with a non-string data type. It crashes currently.

test/parallel/test-vfs.js

@@ -0,0 +1,88 @@
+'use strict';
+constcommon=require('../common');
+
+// This tests the creation of a vfs by monkey-patching fs and Module._stat.
+
+constModule=require('module');
+constfs=require('fs');
+consttmpdir=require('../common/tmpdir');
+const{ deepStrictEqual, ok, strictEqual, throws }=require('assert');
+const{ join }=require('path');
+
+constdirectory=join(tmpdir.path,'directory');
+constdoesNotExist=join(tmpdir.path,'does-not-exist');
+constfile=join(tmpdir.path,'file.js');
+
+tmpdir.refresh();
+fs.writeFileSync(file,"module.exports = { a: 'b' }");
+fs.mkdirSync(directory);
+
+strictEqual(Module._stat(directory),1);
+ok(Module._stat(doesNotExist)<0);
+strictEqual(Module._stat(file),0);
+
+constvfsDirectory=join(process.execPath,'directory');
+constvfsDoesNotExist=join(process.execPath,'does-not-exist');
+constvfsFile=join(process.execPath,'file.js');
+
+ok(Module._stat(vfsDirectory)<0);
+ok(Module._stat(vfsDoesNotExist)<0);
+ok(Module._stat(vfsFile)<0);
+
+deepStrictEqual(require(file),{a: 'b'});
+throws(()=>require(vfsFile),{code: 'MODULE_NOT_FOUND'});
+
+common.expectWarning(
+'ExperimentalWarning',
+'Module._stat is an experimental feature. This feature could change at any time');
+
+process.on('warning',common.mustCall());
+
+constoriginalStat=Module._stat;
+Module._stat=function(filename){
+if(!filename.startsWith(process.execPath)){
+returnoriginalStat(filename);
+}
+
+if(filename===process.execPath){
+return1;
+}
+
+switch(filename){
+casevfsDirectory:
+return1;
+casevfsDoesNotExist:
+return-2;
+casevfsFile:
+return0;
+}
+};
+
+constoriginalReadFileSync=fs.readFileSync;
+// TODO(aduh95): We'd like to have a better way to achieve this without monkey-patching fs.
+fs.readFileSync=functionreadFileSync(pathArgument,options){
+if(!pathArgument.startsWith(process.execPath)){
+returnoriginalReadFileSync.apply(this,arguments);
+}
+if(pathArgument===vfsFile){
+return"module.exports = { x: 'y' };";
+}
+thrownewError();
+};
+
+fs.realpathSync=functionrealpathSync(pathArgument,options){
+returnpathArgument;
+};
+
+strictEqual(Module._stat(directory),1);
+ok(Module._stat(doesNotExist)<0);
+strictEqual(Module._stat(file),0);
+
+strictEqual(Module._stat(vfsDirectory),1);
+ok(Module._stat(vfsDoesNotExist)<0);
+strictEqual(Module._stat(vfsFile),0);
+
+strictEqual(Module._stat(process.execPath),1);
+
+deepStrictEqual(require(file),{a: 'b'});
+deepStrictEqual(require(vfsFile),{x: 'y'});