fix #2331: use ||= to make global names shorter

CHANGELOG.md

@@ -1,5 +1,22 @@
 # Changelog
 
+## Unreleased
+
+* Make global names more compact when `||=` is available ([#2331](https://github.com/evanw/esbuild/issues/2331))
+
+    With this release, the code esbuild generates for the `--global-name=` setting is now slightly shorter when you don't configure esbuild such that the `||=` operator is unsupported (e.g. with `--target=chrome80` or `--supported:logical-assignment=false`):
+
+    ```js
+    // Original code
+    exports.foo = 123
+
+    // Old output (with --format=iife --global-name=foo.bar.baz --minify)
+    var foo=foo||{};foo.bar=foo.bar||{};foo.bar.baz=(()=>{var b=(a,o)=>()=>(o||a((o={exports:{}}).exports,o),o.exports);var c=b(f=>{f.foo=123});return c();})();
+
+    // New output (with --format=iife --global-name=foo.bar.baz --minify)
+    var foo;((foo||={}).bar||={}).baz=(()=>{var b=(a,o)=>()=>(o||a((o={exports:{}}).exports,o),o.exports);var c=b(f=>{f.foo=123});return c();})();
+    ```
+
 ## 0.14.46
 
 * Add the ability to override support for individual syntax features ([#2060](https://github.com/evanw/esbuild/issues/2060), [#2290](https://github.com/evanw/esbuild/issues/2290), [#2308](https://github.com/evanw/esbuild/issues/2308))

internal/bundler/linker.go

@@ -5131,7 +5131,8 @@ func (c *linkerContext) generateChunkJS(chunks []chunkInfo, chunkIndex int, chun
 
 func (c *linkerContext) generateGlobalNamePrefix() string {
 	var text string
-	prefix := c.options.GlobalName[0]
+	globalName := c.options.GlobalName
+	prefix := globalName[0]
 	space := " "
 	join := ";\n"
 
@@ -5140,6 +5141,31 @@ func (c *linkerContext) generateGlobalNamePrefix() string {
 		join = ";"
 	}
 
+	// Use "||=" to make the code more compact when it's supported
+	if len(globalName) > 1 && !c.options.UnsupportedJSFeatures.Has(compat.LogicalAssignment) {
+		if js_printer.CanEscapeIdentifier(prefix, c.options.UnsupportedJSFeatures, c.options.ASCIIOnly) {
+			if c.options.ASCIIOnly {
+				prefix = string(js_printer.QuoteIdentifier(nil, prefix, c.options.UnsupportedJSFeatures))
+			}
+			text = fmt.Sprintf("var %s%s", prefix, join)
+		} else {
+			prefix = fmt.Sprintf("this[%s]", js_printer.QuoteForJSON(prefix, c.options.ASCIIOnly))
+		}
+		for _, name := range globalName[1:] {
+			var dotOrIndex string
+			if js_printer.CanEscapeIdentifier(name, c.options.UnsupportedJSFeatures, c.options.ASCIIOnly) {
+				if c.options.ASCIIOnly {
+					name = string(js_printer.QuoteIdentifier(nil, name, c.options.UnsupportedJSFeatures))
+				}
+				dotOrIndex = fmt.Sprintf(".%s", name)
+			} else {
+				dotOrIndex = fmt.Sprintf("[%s]", js_printer.QuoteForJSON(name, c.options.ASCIIOnly))
+			}
+			prefix = fmt.Sprintf("(%s%s||=%s{})%s", prefix, space, space, dotOrIndex)
+		}
+		return fmt.Sprintf("%s%s%s=%s", text, prefix, space, space)
+	}
+
 	if js_printer.CanEscapeIdentifier(prefix, c.options.UnsupportedJSFeatures, c.options.ASCIIOnly) {
 		if c.options.ASCIIOnly {
 			prefix = string(js_printer.QuoteIdentifier(nil, prefix, c.options.UnsupportedJSFeatures))
@@ -5150,7 +5176,7 @@ func (c *linkerContext) generateGlobalNamePrefix() string {
 		text = fmt.Sprintf("%s%s=%s", prefix, space, space)
 	}
 
-	for _, name := range c.options.GlobalName[1:] {
+	for _, name := range globalName[1:] {
 		oldPrefix := prefix
 		if js_printer.CanEscapeIdentifier(name, c.options.UnsupportedJSFeatures, c.options.ASCIIOnly) {
 			if c.options.ASCIIOnly {

scripts/js-api-tests.js

@@ -3792,14 +3792,34 @@ let transformTests = {
     vm.createContext(globals)
     vm.runInContext(code, globals)
     assert.strictEqual(globals.π["π 𐀀"].𐀀["𐀀 π"].default, 123)
+    assert.strictEqual(code.slice(0, code.indexOf('(() => {\n')), `var \\u03C0;
+(((\\u03C0 ||= {})["\\u03C0 \\uD800\\uDC00"] ||= {})["\\uD800\\uDC00"] ||= {})["\\uD800\\uDC00 \\u03C0"] = `)
+  },
+
+  async iifeGlobalNameUnicodeNoEscape({ esbuild }) {
+    const { code } = await esbuild.transform(`export default 123`, { format: 'iife', globalName: 'π["π 𐀀"].𐀀["𐀀 π"]', charset: 'utf8' })
+    const globals = {}
+    vm.createContext(globals)
+    vm.runInContext(code, globals)
+    assert.strictEqual(globals.π["π 𐀀"].𐀀["𐀀 π"].default, 123)
+    assert.strictEqual(code.slice(0, code.indexOf('(() => {\n')), `var π;
+(((π ||= {})["π 𐀀"] ||= {})["𐀀"] ||= {})["𐀀 π"] = `)
+  },
+
+  async iifeGlobalNameUnicodeEscapeNoLogicalAssignment({ esbuild }) {
+    const { code } = await esbuild.transform(`export default 123`, { format: 'iife', globalName: 'π["π 𐀀"].𐀀["𐀀 π"]', supported: { 'logical-assignment': false } })
+    const globals = {}
+    vm.createContext(globals)
+    vm.runInContext(code, globals)
+    assert.strictEqual(globals.π["π 𐀀"].𐀀["𐀀 π"].default, 123)
     assert.strictEqual(code.slice(0, code.indexOf('(() => {\n')), `var \\u03C0 = \\u03C0 || {};
 \\u03C0["\\u03C0 \\uD800\\uDC00"] = \\u03C0["\\u03C0 \\uD800\\uDC00"] || {};
 \\u03C0["\\u03C0 \\uD800\\uDC00"]["\\uD800\\uDC00"] = \\u03C0["\\u03C0 \\uD800\\uDC00"]["\\uD800\\uDC00"] || {};
 \\u03C0["\\u03C0 \\uD800\\uDC00"]["\\uD800\\uDC00"]["\\uD800\\uDC00 \\u03C0"] = `)
   },
 
-  async iifeGlobalNameUnicodeNoEscape({ esbuild }) {
-    const { code } = await esbuild.transform(`export default 123`, { format: 'iife', globalName: 'π["π 𐀀"].𐀀["𐀀 π"]', charset: 'utf8' })
+  async iifeGlobalNameUnicodeNoEscapeNoLogicalAssignment({ esbuild }) {
+    const { code } = await esbuild.transform(`export default 123`, { format: 'iife', globalName: 'π["π 𐀀"].𐀀["𐀀 π"]', supported: { 'logical-assignment': false }, charset: 'utf8' })
     const globals = {}
     vm.createContext(globals)
     vm.runInContext(code, globals)