Fix stack message missing caused by visit and invoke stack getter bef…

…ore call `captureStackTrace` (found in node V6.x).

Use strict mode.

Prettify tests.

lib/MemoryFileSystemError.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const operationMatchReg = new RegExp("at\\sMemoryFileSystem\\.([^\\s_]+)\\s");
 
 class MemoryFileSystemError extends Error {
@@ -29,10 +31,16 @@ class MemoryFileSystemError extends Error {
 		}
 	}
 	findOperation() {
-		if(!this.stack) return null;
-		var stacks = this.stack.split(/[\r\n|\n][\s]*/);
-		var operation;
+		// use a new obj to capture and inspect stack, because the message \
+		// isn't ready yet, shouldn't invoke stack getter at this time.
+		var captureObj = {};
+		if(Error.captureStackTrace) {
+			Error.captureStackTrace(captureObj);
+		}
+		if(!captureObj.stack) return null;
+		var stacks = captureObj.stack.split(/[\r\n|\n][\s]*/);
 		var findDepth = 1;
+		var operation;
 		while(!operation && findDepth < stacks.length) {
 			var stack = stacks[findDepth];
 			var operationMatch = stack.match(operationMatchReg);
@@ -42,7 +50,7 @@ class MemoryFileSystemError extends Error {
 			findDepth += 1;
 		}
 
-		return operation || null;
+		return operation;
 	}
 }
 

test/MemoryFileSystem.js

@@ -95,15 +95,6 @@ describe("files", function() {
 	});
 });
 describe("errors", function() {
-	function catchError(fn) {
-		try {
-			fn();
-		} catch(e) {
-			return e;
-		}
-		return null;
-	}
-
 	it("should fail on invalid paths", function() {
 		var fs = new MemoryFileSystem();
 		fs.mkdirpSync("/test/a/b/c");
@@ -152,30 +143,6 @@ describe("errors", function() {
 			err.should.be.instanceof(Error);
 		});
 	});
-	it("should include the path in Error message", function(done) {
-		var fs = new MemoryFileSystem();
-		var invalidPath = "/nonexist/file";
-		var error = catchError(function() {
-			fs.statSync(invalidPath);
-		});
-		error.message.indexOf(invalidPath).should.be.above(-1);
-
-		fs.readFile(invalidPath, function(err) {
-			err.message.indexOf(invalidPath).should.be.above(-1);
-			done();
-		});
-	});
-	it("should use correct error name and message in the first line of Error stack", function(done) {
-		var fs = new MemoryFileSystem();
-		fs.unlink("/test/abcd", function(error) {
-			error.should.be.instanceof(Error);
-			var firstLine = error.stack.split(/\r\n|\n/)[0];
-			firstLine.should.startWith(error.name);
-			firstLine.indexOf(error.code).should.be.above(-1);
-			firstLine.indexOf(error.message).should.be.above(-1);
-			done();
-		});
-	});
 	it("should fail incorrect arguments", function() {
 		var fs = new MemoryFileSystem();
 		(function() {

test/MemoryFileSystemError.js

@@ -0,0 +1,51 @@
+var bl = require("bl");
+var should = require("should");
+var MemoryFileSystem = require("../lib/MemoryFileSystem");
+var MemoryFileSystemError = require("../lib/MemoryFileSystemError");
+
+describe("error", function() {
+	function catchError(fn) {
+		try {
+			fn();
+		} catch(e) {
+			return e;
+		}
+		return null;
+	}
+
+	it("should include the path in Error message", function(done) {
+		var fs = new MemoryFileSystem();
+		var invalidPath = "/nonexist/file";
+		var error = catchError(function() {
+			fs.statSync(invalidPath);
+		});
+		error.message.should.containEql(invalidPath);
+
+		fs.readFile(invalidPath, function(err) {
+			err.message.should.containEql(invalidPath);
+			done();
+		});
+	});
+	it("should use correct error message in the first line of Error stack", function(done) {
+		var fs = new MemoryFileSystem();
+		fs.unlink("/test/abcd", function(error) {
+			error.should.be.instanceof(Error);
+			error.stack.should.startWith(error.name);
+
+			var firstLine = error.stack.split(/\r\n|\n/)[0];
+			firstLine.should.containEql(error.code);
+			firstLine.should.containEql(error.message);
+			done();
+		});
+	});
+	it("should work fine without path and operation", function() {
+		var errorData = {
+			code:"ETEST",
+			description:"testerror",
+		};
+		var error = new MemoryFileSystemError(errorData);
+		error.message.should.startWith(error.code);
+		error.stack.should.startWith(error.name);
+		error.stack.should.containEql(error.message);
+	});
+});