fix #2036: strip unsupported import() assertions

CHANGELOG.md

@@ -1,5 +1,22 @@
 # Changelog
 
+## Unreleased
+
+* Strip import assertions from unrecognized `import()` expressions ([#2036](https://github.com/evanw/esbuild/issues/2036))
+
+    The new "import assertions" JavaScript language feature adds an optional second argument to dynamic `import()` expressions, which esbuild does support. However, this optional argument must be stripped when targeting older JavaScript environments for which this second argument would be a syntax error. Previously esbuild failed to strip this second argument in cases when the first argument to `import()` wasn't a string literal. This problem is now fixed:
+
+    ```js
+    // Original code
+    console.log(import(foo, { assert: { type: 'json' } }))
+
+    // Old output (with --target=es6)
+    console.log(import(foo, { assert: { type: "json" } }));
+
+    // New output (with --target=es6)
+    console.log(import(foo));
+    ```
+
 ## 0.14.23
 
 * Update feature database to indicate that node 16.14+ supports import assertions ([#2030](https://github.com/evanw/esbuild/issues/2030))

internal/js_parser/js_parser_test.go

@@ -4741,6 +4741,9 @@ func TestImportAssertions(t *testing.T) {
 	expectPrinted(t, "import(x ? 'y' : 'z', {assert: {x: 1}})", "import(x ? \"y\" : \"z\", { assert: { x: 1 } });\n")
 
 	expectPrintedTarget(t, 2015, "import 'x' assert {x: 'y'}", "import \"x\";\n")
+	expectPrintedTarget(t, 2015, "import(x, {assert: {x: 'y'}})", "import(x);\n")
+	expectPrintedTarget(t, 2015, "import(x, {assert: {x: 1}})", "import(x);\n")
+	expectPrintedTarget(t, 2015, "import(x ? 'y' : 'z', {assert: {x: 'y'}})", "x ? import(\"y\") : import(\"z\");\n")
 	expectPrintedTarget(t, 2015, "import(x ? 'y' : 'z', {assert: {x: 1}})", "import(x ? \"y\" : \"z\");\n")
 	expectParseErrorTarget(t, 2015, "import(x ? 'y' : 'z', {assert: {x: foo()}})",
 		"<stdin>: ERROR: Using an arbitrary value as the second argument to \"import()\" is not possible in the configured target environment\n")

internal/js_printer/js_printer.go

@@ -1890,11 +1890,14 @@ func (p *printer) printExpr(expr js_ast.Expr, level js_ast.L, flags printExprFla
 			p.printIndent()
 		}
 		p.printExpr(e.Expr, js_ast.LComma, 0)
-		if e.OptionsOrNil.Data != nil {
+
+		// Just omit import assertions if they aren't supported
+		if e.OptionsOrNil.Data != nil && !p.options.UnsupportedFeatures.Has(compat.ImportAssertions) {
 			p.print(",")
 			p.printSpace()
 			p.printExpr(e.OptionsOrNil, js_ast.LComma, 0)
 		}
+
 		if len(leadingInteriorComments) > 0 {
 			p.printNewline()
 			p.options.Indent--