Merge pull request #179 from Osamaali313/fix/boolean-flag-explicit-value

fix(args): honor explicit value on boolean flags (--flag=false)

Author: NianJiuZst

src/args.ts

@@ -1,6 +1,10 @@
 import type { GlobalFlags } from './types/flags';
 import type { OptionDef } from './command';
 
+/** Recognised spellings for an explicit boolean flag value, e.g. `--flag=false`. */
+const BOOLEAN_TRUE_VALUES = new Set(['true', '1', 'yes', 'on']);
+const BOOLEAN_FALSE_VALUES = new Set(['false', '0', 'no', 'off']);
+
 function kebabToCamel(str: string): string {
   return str.replace(/-([a-z])/g, (_, c: string) => c.toUpperCase());
 }
@@ -114,7 +118,23 @@ export function parseFlags(argv: string[], options: OptionDef[]): GlobalFlags {
       const camelKey = kebabToCamel(key);
 
       if (schema.booleans.has(camelKey)) {
-        (flags as Record<string, unknown>)[camelKey] = true;
+        // A bare boolean flag (`--flag`) is true. Honour an explicit value
+        // (`--flag=false`, `--flag=0`, ...) and reject an unrecognised one so a
+        // typo cannot silently enable the flag, mirroring numeric-flag handling.
+        if (value === undefined) {
+          (flags as Record<string, unknown>)[camelKey] = true;
+        } else {
+          const normalized = value.trim().toLowerCase();
+          if (BOOLEAN_TRUE_VALUES.has(normalized)) {
+            (flags as Record<string, unknown>)[camelKey] = true;
+          } else if (BOOLEAN_FALSE_VALUES.has(normalized)) {
+            (flags as Record<string, unknown>)[camelKey] = false;
+          } else {
+            throw new Error(
+              `Flag --${key} requires a boolean value (e.g. true/false), got "${value}".`,
+            );
+          }
+        }
         i++;
         continue;
       }

test/args.test.ts

@@ -5,6 +5,7 @@ import type { OptionDef } from '../src/command';
 const OPTIONS: OptionDef[] = [
   { flag: '--timeout <seconds>', description: 'Request timeout', type: 'number' },
   { flag: '--message <text>', description: 'Message text', type: 'array' },
+  { flag: '--verbose', description: 'Verbose output' },
 ];
 
 describe('parseFlags', () => {
@@ -25,4 +26,30 @@ describe('parseFlags', () => {
 
     expect(flags.timeout).toBe(1.5);
   });
+
+  it('treats a bare boolean flag as true', () => {
+    expect(parseFlags(['--verbose'], OPTIONS).verbose).toBe(true);
+  });
+
+  it('honours explicit false-like values on a boolean flag', () => {
+    // Regression: `--flag=false` / `--flag=0` were silently set to true.
+    for (const v of ['false', '0', 'no', 'off', ' OFF ', 'False']) {
+      expect(parseFlags([`--verbose=${v}`], OPTIONS).verbose).toBe(false);
+    }
+  });
+
+  it('honours explicit true-like values on a boolean flag', () => {
+    for (const v of ['true', '1', 'yes', 'on', 'TRUE']) {
+      expect(parseFlags([`--verbose=${v}`], OPTIONS).verbose).toBe(true);
+    }
+  });
+
+  it('rejects an unrecognised explicit boolean value', () => {
+    expect(() => parseFlags(['--verbose=maybe'], OPTIONS)).toThrow(
+      'Flag --verbose requires a boolean value',
+    );
+    expect(() => parseFlags(['--verbose='], OPTIONS)).toThrow(
+      'Flag --verbose requires a boolean value',
+    );
+  });
 });