From 2820c325e0fbcdaaf4eb436bea6afdfb8ce24291 Mon Sep 17 00:00:00 2001
From: Nash Aschenbath <wwh86696@163.com>
Date: Mon, 9 Nov 2026 03:27:21 +0800
Subject: [PATCH 1/2] Preserve equals signs in define mapping values

---
 src/lib/option-normalization.js          |  6 ++-
 test/__snapshots__/index.test.js.snap    | 24 ++++++++++
 test/fixtures/define-equals/index.js     |  6 +++
 test/fixtures/define-equals/package.json |  6 +++
 test/option-normalization.test.js        | 60 ++++++++++++++++++++++++
 5 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 test/fixtures/define-equals/index.js
 create mode 100644 test/fixtures/define-equals/package.json
 create mode 100644 test/option-normalization.test.js

diff --git a/src/lib/option-normalization.js b/src/lib/option-normalization.js
index 22811039..9881f3d0 100644
--- a/src/lib/option-normalization.js
+++ b/src/lib/option-normalization.js
@@ -29,7 +29,11 @@ export function toReplacementExpression(value, name) {
 export function parseMappingArgument(globalStrings, processValue) {
 	const globals = {};
 	globalStrings.split(',').forEach(globalString => {
-		let [key, value] = globalString.split('=');
+		const separator = globalString.indexOf('=');
+		let key =
+			separator === -1 ? globalString : globalString.slice(0, separator);
+		let value =
+			separator === -1 ? undefined : globalString.slice(separator + 1);
 		if (processValue) {
 			const r = processValue(value, key);
 			if (r !== undefined) {
diff --git a/test/__snapshots__/index.test.js.snap b/test/__snapshots__/index.test.js.snap
index 27dedc37..2664cdcd 100644
--- a/test/__snapshots__/index.test.js.snap
+++ b/test/__snapshots__/index.test.js.snap
@@ -1810,6 +1810,30 @@ exports[`fixtures build define with microbundle 5`] = `
 "
 `;
 
+exports[`fixtures build define-equals with microbundle 1`] = `
+"Used script: microbundle --no-sourcemap -f cjs --define \\"TOKEN='abc==',URL='https://example.test/?key=value=tail',@IS_EQUAL=(1===1),@INCREMENT=(value=>value+1)\\"
+
+Directory tree:
+
+define-equals
+  dist
+    define-equals.js
+  index.js
+  package.json
+
+
+Build \\"define-equals\\" to dist:
+112 B: define-equals.js.gz
+91 B: define-equals.js.br"
+`;
+
+exports[`fixtures build define-equals with microbundle 2`] = `1`;
+
+exports[`fixtures build define-equals with microbundle 3`] = `
+"module.exports={token:\\"abc==\\",url:\\"https://example.test/?key=value=tail\\",equal:!0,incremented:3};
+"
+`;
+
 exports[`fixtures build define-expression with microbundle 1`] = `
 "Used script: microbundle -f esm --no-sourcemap --define @Object.freeze=Object
 
diff --git a/test/fixtures/define-equals/index.js b/test/fixtures/define-equals/index.js
new file mode 100644
index 00000000..e82af6c0
--- /dev/null
+++ b/test/fixtures/define-equals/index.js
@@ -0,0 +1,6 @@
+export default {
+	token: TOKEN,
+	url: URL,
+	equal: IS_EQUAL,
+	incremented: INCREMENT(2),
+};
diff --git a/test/fixtures/define-equals/package.json b/test/fixtures/define-equals/package.json
new file mode 100644
index 00000000..1682c905
--- /dev/null
+++ b/test/fixtures/define-equals/package.json
@@ -0,0 +1,6 @@
+{
+  "name": "define-equals",
+  "scripts": {
+    "build": "microbundle --no-sourcemap -f cjs --define \"TOKEN='abc==',URL='https://example.test/?key=value=tail',@IS_EQUAL=(1===1),@INCREMENT=(value=>value+1)\""
+  }
+}
diff --git a/test/option-normalization.test.js b/test/option-normalization.test.js
new file mode 100644
index 00000000..4e53e4a6
--- /dev/null
+++ b/test/option-normalization.test.js
@@ -0,0 +1,60 @@
+import {
+	parseMappingArgument,
+	toReplacementExpression,
+} from '../src/lib/option-normalization';
+
+describe('mapping arguments', () => {
+	it.each([
+		['TOKEN=abc==', { TOKEN: 'abc==' }],
+		[
+			'URL=https://example.test/?key=value=tail',
+			{ URL: 'https://example.test/?key=value=tail' },
+		],
+		['VALUE==', { VALUE: '=' }],
+		[
+			'VALUE=first=second\nthird=fourth',
+			{ VALUE: 'first=second\nthird=fourth' },
+		],
+	])('preserves equals signs in %s', (input, expected) => {
+		expect(parseMappingArgument(input)).toEqual(expected);
+	});
+
+	it.each([
+		['TOKEN=abc==', { TOKEN: '"abc=="' }],
+		["TOKEN='abc=='", { TOKEN: '"abc=="' }],
+		['TOKEN="abc=="', { TOKEN: '"abc=="' }],
+		['@IS_EQUAL=1===1', { IS_EQUAL: '1===1' }],
+		['@INCREMENT=value=>value+1', { INCREMENT: 'value=>value+1' }],
+	])('preserves define values in %s', (input, expected) => {
+		expect(parseMappingArgument(input, toReplacementExpression)).toEqual(
+			expected,
+		);
+	});
+
+	it('keeps neighboring definitions and literal conversion', () => {
+		expect(
+			parseMappingArgument(
+				'A=true,TOKEN=abc==,B=42,C=false',
+				toReplacementExpression,
+			),
+		).toEqual({ A: 'true', TOKEN: '"abc=="', B: '42', C: 'false' });
+	});
+
+	it('keeps empty and missing values distinct', () => {
+		expect(parseMappingArgument('EMPTY=,MISSING')).toEqual({
+			EMPTY: '',
+			MISSING: undefined,
+		});
+	});
+
+	it('passes the complete value and key to the processor', () => {
+		const process = jest.fn((value, key) => [
+			value.toUpperCase(),
+			key.toLowerCase(),
+		]);
+		expect(parseMappingArgument('TOKEN=abc==', process)).toEqual({
+			token: 'ABC==',
+		});
+		expect(process).toHaveBeenCalledWith('abc==', 'TOKEN');
+	});
+});

From 4f21a2cd3b6e12987f982edada7ae0a84304cfd7 Mon Sep 17 00:00:00 2001
From: Nash Aschenbath <wwh86696@163.com>
Date: Mon, 9 Nov 2026 08:56:26 +0800
Subject: [PATCH 2/2] Add patch changeset for complete define values

---
 .changeset/tame-tokens-keep.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/tame-tokens-keep.md

diff --git a/.changeset/tame-tokens-keep.md b/.changeset/tame-tokens-keep.md
new file mode 100644
index 00000000..f24b62af
--- /dev/null
+++ b/.changeset/tame-tokens-keep.md
@@ -0,0 +1,5 @@
+---
+'microbundle': patch
+---
+
+Preserve equals signs in `--define` values, including padded tokens and equality or arrow expressions.