Add isRegExp type guard (#3647)

Effect-TS · Sep 25, 2024 · 24eb357 · 24eb357
1 parent 1c36c3f
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diff --git a/.changeset/tricky-oranges-melt.md b/.changeset/tricky-oranges-melt.md
@@ -0,0 +1,5 @@
+---
+"effect": minor
+---
+
+Add an `isRegExp` type guard
diff --git a/packages/effect/dtslint/Predicate.ts b/packages/effect/dtslint/Predicate.ts
@@ -194,6 +194,13 @@ if (Predicate.isTupleOfAtLeast(unknowns, 3)) {
   unknowns
 }
 
+// -------------------------------------------------------------------------------------
+// isRegExp
+// -------------------------------------------------------------------------------------
+
+// $ExpectType RegExp[]
+unknowns.filter(Predicate.isRegExp)
+
 // -------------------------------------------------------------------------------------
 // compose
 // -------------------------------------------------------------------------------------

diff --git a/packages/effect/src/Predicate.ts b/packages/effect/src/Predicate.ts
@@ -665,6 +665,22 @@ export const isPromiseLike = (
   input: unknown
 ): input is PromiseLike<unknown> => hasProperty(input, "then") && isFunction(input.then)
 
+/**
+ * Tests if a value is a `RegExp`.
+ *
+ * @param input - The value to test.
+ *
+ * @example
+ * import { Predicate } from "effect"
+ *
+ * assert.deepStrictEqual(Predicate.isRegExp(/a/), true)
+ * assert.deepStrictEqual(Predicate.isRegExp("a"), false)
+ *
+ * @category guards
+ * @since 3.9.0
+ */
+export const isRegExp = (input: unknown): input is RegExp => input instanceof RegExp
+
 /**
  * @since 2.0.0
  */

diff --git a/packages/effect/src/RegExp.ts b/packages/effect/src/RegExp.ts
@@ -3,6 +3,23 @@
  *
  * @since 2.0.0
  */
+import * as predicate from "./Predicate.js"
+
+/**
+ * Tests if a value is a `RegExp`.
+ *
+ * @param input - The value to test.
+ *
+ * @example
+ * import { RegExp } from "effect"
+ *
+ * assert.deepStrictEqual(RegExp.isRegExp(/a/), true)
+ * assert.deepStrictEqual(RegExp.isRegExp("a"), false)
+ *
+ * @category guards
+ * @since 3.9.0
+ */
+export const isRegExp: (input: unknown) => input is RegExp = predicate.isRegExp
 
 /**
  * Escapes special characters in a regular expression pattern.

diff --git a/packages/effect/test/Predicate.test.ts b/packages/effect/test/Predicate.test.ts
@@ -334,4 +334,10 @@ describe("Predicate", () => {
     assert.deepStrictEqual(_.isTupleOfAtLeast([1, 2, 3], 2), true)
     assert.deepStrictEqual(_.isTupleOfAtLeast([1, 2, 3], 4), false)
   })
+
+  it("isRegExp", () => {
+    assert.deepStrictEqual(_.isRegExp(/a/), true)
+    assert.deepStrictEqual(_.isRegExp(null), false)
+    assert.deepStrictEqual(_.isRegExp("a"), false)
+  })
 })
diff --git a/packages/effect/test/RegExp.test.ts b/packages/effect/test/RegExp.test.ts
@@ -2,6 +2,12 @@ import * as RegExp from "effect/RegExp"
 import { describe, expect, it } from "vitest"
 
 describe("RegExp", () => {
+  it("isRegExp", () => {
+    expect(RegExp.isRegExp(/a/)).toEqual(true)
+    expect(RegExp.isRegExp(null)).toEqual(false)
+    expect(RegExp.isRegExp("a")).toEqual(false)
+  })
+
   describe("escape", () => {
     it("should escape special characters correctly", () => {
       const testCases: Array<[string, string]> = [