2 files changed, 149 insertions, 2 deletions

diff --git a/fs/glob.ts b/fs/glob.ts
index e7e5aee21..8d322b761 100644
--- a/fs/glob.ts
+++ b/fs/glob.ts
@@ -43,3 +43,35 @@ export interface GlobOptions {
 export function glob(glob: string, options: GlobOptions = {}): RegExp {
   return globrex(glob, options).regex;
 }
+
+/** Test whether the given string is a glob */
+export function isGlob(str: string): boolean {
+  const chars: Record<string, string> = { "{": "}", "(": ")", "[": "]" };
+  const regex = /\\(.)|(^!|\*|[\].+)]\?|\[[^\\\]]+\]|\{[^\\}]+\}|\(\?[:!=][^\\)]+\)|\([^|]+\|[^\\)]+\))/;
+
+  if (str === "") {
+    return false;
+  }
+
+  let match: RegExpExecArray | null;
+
+  while ((match = regex.exec(str))) {
+    if (match[2]) return true;
+    let idx = match.index + match[0].length;
+
+    // if an open bracket/brace/paren is escaped,
+    // set the index to the next closing character
+    const open = match[1];
+    const close = open ? chars[open] : null;
+    if (open && close) {
+      const n = str.indexOf(close, idx);
+      if (n !== -1) {
+        idx = n + 1;
+      }
+    }
+
+    str = str.slice(idx);
+  }
+
+  return false;
+}
diff --git a/fs/glob_test.ts b/fs/glob_test.ts
index 3139cb7f4..9151b9e9e 100644
--- a/fs/glob_test.ts
+++ b/fs/glob_test.ts
@@ -1,8 +1,8 @@
 const { mkdir } = Deno;
 type FileInfo = Deno.FileInfo;
 import { test, runIfMain } from "../testing/mod.ts";
-import { assertEquals } from "../testing/asserts.ts";
-import { glob } from "./glob.ts";
+import { assert, assertEquals } from "../testing/asserts.ts";
+import { glob, isGlob } from "./glob.ts";
 import { join } from "./path.ts";
 import { testWalk } from "./walk_test.ts";
 import { touch, walkArray } from "./walk_test.ts";
@@ -138,4 +138,119 @@ testWalk(
   }
 );
 
+test({
+  name: "isGlob: pattern to test",
+  fn(): void {
+    // should be true if valid glob pattern
+    assert(isGlob("!foo.js"));
+    assert(isGlob("*.js"));
+    assert(isGlob("!*.js"));
+    assert(isGlob("!foo"));
+    assert(isGlob("!foo.js"));
+    assert(isGlob("**/abc.js"));
+    assert(isGlob("abc/*.js"));
+    assert(isGlob("@.(?:abc)"));
+    assert(isGlob("@.(?!abc)"));
+
+    // should be false if invalid glob pattern
+    assert(!isGlob(""));
+    assert(!isGlob("~/abc"));
+    assert(!isGlob("~/abc"));
+    assert(!isGlob("~/(abc)"));
+    assert(!isGlob("+~(abc)"));
+    assert(!isGlob("."));
+    assert(!isGlob("@.(abc)"));
+    assert(!isGlob("aa"));
+    assert(!isGlob("who?"));
+    assert(!isGlob("why!?"));
+    assert(!isGlob("where???"));
+    assert(!isGlob("abc!/def/!ghi.js"));
+    assert(!isGlob("abc.js"));
+    assert(!isGlob("abc/def/!ghi.js"));
+    assert(!isGlob("abc/def/ghi.js"));
+
+    // Should be true if path has regex capture group
+    assert(isGlob("abc/(?!foo).js"));
+    assert(isGlob("abc/(?:foo).js"));
+    assert(isGlob("abc/(?=foo).js"));
+    assert(isGlob("abc/(a|b).js"));
+    assert(isGlob("abc/(a|b|c).js"));
+    assert(isGlob("abc/(foo bar)/*.js"));
+
+    // Should be false if the path has parens but is not a valid capture group
+    assert(!isGlob("abc/(?foo).js"));
+    assert(!isGlob("abc/(a b c).js"));
+    assert(!isGlob("abc/(ab).js"));
+    assert(!isGlob("abc/(abc).js"));
+    assert(!isGlob("abc/(foo bar).js"));
+
+    // should be false if the capture group is imbalanced
+    assert(!isGlob("abc/(?ab.js"));
+    assert(!isGlob("abc/(ab.js"));
+    assert(!isGlob("abc/(a|b.js"));
+    assert(!isGlob("abc/(a|b|c.js"));
+
+    // should be true if the path has a regex character class
+    assert(isGlob("abc/[abc].js"));
+    assert(isGlob("abc/[^abc].js"));
+    assert(isGlob("abc/[1-3].js"));
+
+    // should be false if the character class is not balanced
+    assert(!isGlob("abc/[abc.js"));
+    assert(!isGlob("abc/[^abc.js"));
+    assert(!isGlob("abc/[1-3.js"));
+
+    // should be false if the character class is escaped
+    assert(!isGlob("abc/\\[abc].js"));
+    assert(!isGlob("abc/\\[^abc].js"));
+    assert(!isGlob("abc/\\[1-3].js"));
+
+    // should be true if the path has brace characters
+    assert(isGlob("abc/{a,b}.js"));
+    assert(isGlob("abc/{a..z}.js"));
+    assert(isGlob("abc/{a..z..2}.js"));
+
+    // should be false if (basic) braces are not balanced
+    assert(!isGlob("abc/\\{a,b}.js"));
+    assert(!isGlob("abc/\\{a..z}.js"));
+    assert(!isGlob("abc/\\{a..z..2}.js"));
+
+    // should be true if the path has regex characters
+    assert(isGlob("!&(abc)"));
+    assert(isGlob("!*.js"));
+    assert(isGlob("!foo"));
+    assert(isGlob("!foo.js"));
+    assert(isGlob("**/abc.js"));
+    assert(isGlob("*.js"));
+    assert(isGlob("*z(abc)"));
+    assert(isGlob("[1-10].js"));
+    assert(isGlob("[^abc].js"));
+    assert(isGlob("[a-j]*[^c]b/c"));
+    assert(isGlob("[abc].js"));
+    assert(isGlob("a/b/c/[a-z].js"));
+    assert(isGlob("abc/(aaa|bbb).js"));
+    assert(isGlob("abc/*.js"));
+    assert(isGlob("abc/{a,b}.js"));
+    assert(isGlob("abc/{a..z..2}.js"));
+    assert(isGlob("abc/{a..z}.js"));
+
+    assert(!isGlob("$(abc)"));
+    assert(!isGlob("&(abc)"));
+    assert(!isGlob("Who?.js"));
+    assert(!isGlob("? (abc)"));
+    assert(!isGlob("?.js"));
+    assert(!isGlob("abc/?.js"));
+
+    // should be false if regex characters are escaped
+    assert(!isGlob("\\?.js"));
+    assert(!isGlob("\\[1-10\\].js"));
+    assert(!isGlob("\\[^abc\\].js"));
+    assert(!isGlob("\\[a-j\\]\\*\\[^c\\]b/c"));
+    assert(!isGlob("\\[abc\\].js"));
+    assert(!isGlob("\\a/b/c/\\[a-z\\].js"));
+    assert(!isGlob("abc/\\(aaa|bbb).js"));
+    assert(!isGlob("abc/\\?.js"));
+  }
+});
+
 runIfMain(import.meta);