fix #1947: improve printing of invalid @import

CHANGELOG.md

@@ -1,5 +1,23 @@
 # Changelog
 
+## Unreleased
+
+* Print invalid CSS differently ([#1947](https://github.com/evanw/esbuild/issues/1947))
+
+    This changes how esbuild prints nested `@import` statements that are missing a trailing `;`, which is invalid CSS. The result is still partially invalid CSS, but now printed in a better-looking way:
+
+    ```css
+    /* Original code */
+    .bad { @import url("other") }
+    .red { background: red; }
+
+    /* Old output (with --minify) */
+    .bad{@import url(other) } .red{background: red;}}
+
+    /* New output (with --minify) */
+    .bad{@import"other";}.red{background:red}
+    ```
+
 ## 0.14.11
 
 * Fix a bug with enum inlining ([#1903](https://github.com/evanw/esbuild/issues/1903))

internal/css_parser/css_parser.go

@@ -665,7 +665,8 @@ func (p *parser) parseAtRule(context atRuleContext) css_ast.Rule {
 		if path, r, ok := p.expectURLOrString(); ok {
 			importConditionsStart := p.index
 			for {
-				if kind := p.current().Kind; kind == css_lexer.TSemicolon || kind == css_lexer.TOpenBrace || kind == css_lexer.TEndOfFile {
+				if kind := p.current().Kind; kind == css_lexer.TSemicolon || kind == css_lexer.TOpenBrace ||
+					kind == css_lexer.TCloseBrace || kind == css_lexer.TEndOfFile {
 					break
 				}
 				p.parseComponentValue()

internal/css_parser/css_parser_test.go

@@ -838,6 +838,9 @@ func TestAtImport(t *testing.T) {
 
 	expectParseError(t, "@import \"foo.css\" {}", "<stdin>: WARNING: Expected \";\"\n")
 	expectPrinted(t, "@import \"foo\"\na { color: red }\nb { color: blue }", "@import \"foo\" a { color: red }\nb {\n  color: blue;\n}\n")
+
+	expectParseError(t, "a { @import \"foo.css\" }", "<stdin>: WARNING: Expected \";\"\n")
+	expectPrinted(t, "a { @import \"foo.css\" }", "a {\n  @import \"foo.css\";\n}\n")
 }
 
 func TestLegalComment(t *testing.T) {