From da61c1de50a59438c4aefa8a3b95839960fb730b Mon Sep 17 00:00:00 2001
From: Chris Wanstrath <chris@ozmm.org>
Date: Sun, 26 Oct 2025 08:24:58 -0700
Subject: [PATCH] isValue()

---
 src/index.ts        |  2 +-
 src/value.ts        |  6 +++-
 tests/value.test.ts | 82 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+), 2 deletions(-)
 create mode 100644 tests/value.test.ts

diff --git a/src/index.ts b/src/index.ts
index 119f0e1..1fab29d 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -13,5 +13,5 @@ export { wrapNative, isWrapped, type ParamInfo, extractParamInfo, getOriginalFun
 export { OpCode } from "./opcode"
 export { Scope } from "./scope"
 export type { Value, TypeScriptFunction, NativeFunction } from "./value"
-export { toValue, toString, toNumber, fromValue, toNull } from "./value"
+export { isValue, toValue, toString, toNumber, fromValue, toNull } from "./value"
 export { VM } from "./vm"
\ No newline at end of file
diff --git a/src/value.ts b/src/value.ts
index 47fe7f9..af1930e 100644
--- a/src/value.ts
+++ b/src/value.ts
@@ -36,11 +36,15 @@ export type FunctionDef = {
   named: boolean
 }
 
+export function isValue(v: any): boolean {
+  return !!(v && typeof v === 'object' && v.type && 'value' in v)
+}
+
 export function toValue(v: any): Value /* throws */ {
   if (v === null || v === undefined)
     return { type: 'null', value: null }
 
-  if (v && typeof v === 'object' && 'type' in v && 'value' in v)
+  if (isValue(v))
     return v as Value
 
   if (Array.isArray(v))
diff --git a/tests/value.test.ts b/tests/value.test.ts
new file mode 100644
index 0000000..193e087
--- /dev/null
+++ b/tests/value.test.ts
@@ -0,0 +1,82 @@
+import { test, expect } from "bun:test"
+import { isValue, toValue } from "#reef"
+
+test("isValue - recognizes valid Value objects", () => {
+  expect(isValue({ type: 'number', value: 42 })).toBe(true)
+  expect(isValue({ type: 'number', value: 0 })).toBe(true)
+  expect(isValue({ type: 'string', value: 'hello' })).toBe(true)
+  expect(isValue({ type: 'string', value: '' })).toBe(true)
+  expect(isValue({ type: 'boolean', value: true })).toBe(true)
+  expect(isValue({ type: 'boolean', value: false })).toBe(true)
+  expect(isValue({ type: 'null', value: null })).toBe(true)
+  expect(isValue({ type: 'array', value: [] })).toBe(true)
+  expect(isValue({ type: 'array', value: [toValue(1), toValue(2)] })).toBe(true)
+  expect(isValue({ type: 'dict', value: new Map() })).toBe(true)
+  expect(isValue({ type: 'regex', value: /test/ })).toBe(true)
+  expect(isValue({
+    type: 'function',
+    value: '<function>',
+    params: [],
+    defaults: {},
+    body: 0,
+    variadic: false,
+    named: false,
+    parentScope: null as any
+  })).toBe(true)
+  expect(isValue({
+    type: 'native',
+    value: '<function>',
+    fn: (() => { }) as any
+  })).toBe(true)
+})
+
+test("isValue - rejects primitives", () => {
+  expect(isValue(42)).toBe(false)
+  expect(isValue(0)).toBe(false)
+  expect(isValue('hello')).toBe(false)
+  expect(isValue('')).toBe(false)
+  expect(isValue(true)).toBe(false)
+  expect(isValue(false)).toBe(false)
+  expect(isValue(null)).toBe(false)
+  expect(isValue(undefined)).toBe(false)
+})
+
+test("isValue - rejects plain objects", () => {
+  expect(isValue({})).toBe(false)
+  expect(isValue({ foo: 'bar' })).toBe(false)
+  expect(isValue({ type: 'number' })).toBe(false)
+  expect(isValue({ value: 42 })).toBe(false)
+})
+
+test("isValue - rejects arrays and functions", () => {
+  expect(isValue([])).toBe(false)
+  expect(isValue([1, 2, 3])).toBe(false)
+  expect(isValue(() => { })).toBe(false)
+  expect(isValue(function () { })).toBe(false)
+})
+
+test("isValue - rejects other object types", () => {
+  expect(isValue(new Date())).toBe(false)
+  expect(isValue(/regex/)).toBe(false)
+  expect(isValue(new Map())).toBe(false)
+  expect(isValue(new Set())).toBe(false)
+})
+
+test("isValue - used by toValue to detect already-converted values", () => {
+  const value = toValue(42)
+  expect(isValue(value)).toBe(true)
+
+  const result = toValue(value)
+  expect(result).toBe(value)
+})
+
+test("isValue - edge cases with type and value properties", () => {
+  // extra properties
+  expect(isValue({ type: 'number', value: 42, extra: 'data' })).toBe(true)
+
+  expect(isValue({ type: null, value: 42 })).toBe(false)
+  expect(isValue({ type: 'number', value: undefined })).toBe(true)
+
+  expect(isValue({ type: 'number', val: 42 })).toBe(false)
+  expect(isValue({ typ: 'number', value: 42 })).toBe(false)
+})