limit brace expansion to 1_000 items

This is usually more than enough, and prevents a potential OOM crash
that will occur with excessively large and complicated brace sections.

The default was already reduced for minimatch down to 100_000, but that
is still too high when dealing with the added complexities of file
system walking.

Also, just because the debugging for this issue was annoying without it,
a custom inspect method is added to the Pattern class.

closes: #533

Author: isaacs

src/glob.ts

@@ -339,6 +339,15 @@ export interface GlobOptions {
    * @default true
    */
   includeChildMatches?: boolean
+
+  /**
+   * max number of `{...}` patterns to expand. Default `1_000`.
+   *
+   * Note: this is much less than minimatch's default of `100_000`,
+   * because Glob has higher memory requirements due to walking
+   * the file system tree.
+   */
+  braceExpandMax?: number
 }
 
 export type GlobOptionsWithFileTypesTrue = GlobOptions & {
@@ -511,11 +520,12 @@ export class Glob<Opts extends GlobOptions> implements GlobOptions {
       this.platform === 'darwin' || this.platform === 'win32'
 
     const mmo: MinimatchOptions = {
-      // default nocase based on platform
+      braceExpandMax: 10_000,
       ...opts,
       dot: this.dot,
       matchBase: this.matchBase,
       nobrace: this.nobrace,
+      // default nocase based on platform
       nocase: this.nocase,
       nocaseMagicOnly,
       nocomment: true,

src/pattern.ts

@@ -20,6 +20,8 @@ const isPatternList = (pl: MMPattern[]): pl is PatternList =>
   pl.length >= 1
 const isGlobList = (gl: string[]): gl is GlobList => gl.length >= 1
 
+const customInspect = Symbol.for('nodejs.util.inspect.custom')
+
 /**
  * An immutable-ish view on an array of glob parts and their parsed
  * results
@@ -102,6 +104,10 @@ export class Pattern {
     }
   }
 
+  [customInspect]() {
+    return 'Pattern <' + this.#globList.slice(this.#index).join('/') + '>'
+  }
+
   /**
    * The first entry in the parsed list of patterns
    */

tap-snapshots/test/pattern.ts.test.cjs

@@ -0,0 +1,18 @@
+/* IMPORTANT
+ * This snapshot file is auto-generated, but designed for humans.
+ * It should be checked into source control and tracked carefully.
+ * Re-generate by setting TAP_SNAPSHOT=1 and running tests.
+ * Make sure to inspect the output below.  Do not ignore changes!
+ */
+'use strict'
+exports[`test/pattern.ts > TAP > g 1`] = `
+Pattern <**>
+`
+
+exports[`test/pattern.ts > TAP > r 1`] = `
+Pattern <?>
+`
+
+exports[`test/pattern.ts > TAP > s 1`] = `
+Pattern <x>
+`

test/oom.ts

@@ -0,0 +1,23 @@
+import t from 'tap'
+import { Glob } from '../src/index.js'
+
+const pattern =
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}' +
+  '{*z,x*y/z*,a*b*}'
+
+t.test('does not oom on long glob', async t => {
+  const g = new Glob(pattern, { braceExpandMax: 1_000 })
+  const results = await g.walk()
+
+  console.error(g)
+  t.pass('did not run out of memory')
+  t.equal(results.length, 0, 'should not find anything')
+})

test/pattern.ts

@@ -2,6 +2,7 @@ import { GLOBSTAR } from 'minimatch'
 import t from 'tap'
 import { MMPattern, Pattern } from '../dist/esm/pattern.js'
 import { Glob } from '../dist/esm/index.js'
+import { inspect } from 'node:util'
 
 t.same(
   new Glob(
@@ -32,6 +33,14 @@ t.throws(() => {
   new Pattern([], ['x'], 0, process.platform)
 })
 
+const p = new Pattern(
+  ['A', 'B', 'C', 'D'],
+  ['a', 'b', 'c', 'd'],
+  1,
+  process.platform,
+)
+t.equal(inspect(p), 'Pattern <b/c/d>')
+
 t.throws(() => {
   new Pattern(['x'], [], 0, process.platform)
 })
@@ -56,6 +65,9 @@ const g = new Pattern(
   process.platform,
 )
 const r = new Pattern([/./], ['?'], 0, process.platform)
+t.matchSnapshot(inspect(s), 's')
+t.matchSnapshot(inspect(r), 'r')
+t.matchSnapshot(inspect(g), 'g')
 t.equal(s.isString(), true)
 t.equal(g.isString(), false)
 t.equal(r.isString(), false)