Update filename character restriction in documention, linter and a few filenames

CONTRIBUTING.md

@@ -10,7 +10,7 @@
 
 Test cases should be created in files that are named to identify the feature or API that's being tested.
 
-There is no strict naming convention. The file names should be human readable, helpful and, ideally, consistent within a single directory. For examples:
+The names should use alphanumeric characters and `.`, `-`, `_`. Otherwise, there is no strict naming convention, but the file names should be human readable, helpful and, ideally, consistent within a single directory. For examples:
 
 - `Math.fround` handling of `Infinity`: `test/built-ins/Math/fround/Math.fround_Infinity.js`
 - `Array.prototype.find` use with `Proxy`: `test/built-ins/Array/prototype/find/Array.prototype.find_callable-Proxy-1.js`

tools/lint/lib/checks/filename.py

@@ -0,0 +1,13 @@
+import re
+
+from ..check import Check
+
+_DISALLOWED_PATTERN = re.compile('[^a-zA-Z0-9/\\-_.]')
+
+class CheckFileName(Check):
+    '''Ensure tests have a valid name.'''
+    ID = 'FILENAME'
+
+    def run(self, name, meta, source):
+        if _DISALLOWED_PATTERN.search(name):
+            return "Contains non-alphanumeric or `-`, `_`, '.' characters."

tools/lint/lint.py

@@ -32,6 +32,7 @@ from lib.checks.frontmatter import CheckFrontmatter
 from lib.checks.harnessfeatures import CheckHarnessFeatures
 from lib.checks.license import CheckLicense
 from lib.checks.negative import CheckNegative
+from lib.checks.filename import CheckFileName
 from lib.eprint import eprint
 import lib.frontmatter
 import lib.whitelist
@@ -46,6 +47,7 @@ parser.add_argument('path',
 
 checks = [
     CheckEsid(),
+    CheckFileName(),
     CheckFrontmatter(),
     CheckFeatures('features.txt'),
     CheckHarnessFeatures(),

tools/lint/test/fixtures/filename_forbidden_char_$.js

@@ -0,0 +1,10 @@
+FILENAME
+^ expected errors | v input
+// Copyright (c) 2018 Valerie Young.  All rights reserved.
+// This code is governed by the license found in the LICENSE file.
+/*---
+esid: sec-assignment-operators-static-semantics-early-errors
+description: Minimal test
+---*/
+
+void 0;