fix(css): ensure code is valid after empty css chunk imports are removed

Make sure that minified code that chains `require` calls with the `,` operator will not result in invalid code when removing
one of the chained requires. Previously the last require that terminates with a semicolon was removed with the semicolon.
This produced invalid code like `require(), /* empty css */const foo =`

Now we append either a comma if a next require call was chained, like
`require(...), require(css), other` --> `require(...)/* empty css */, other`

Or terminate with a semicolon
`require(...), require(css); const foo = ...` --> `require(...)/* empty css */; const foo = ...`

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

packages/vite/src/node/plugins/css.ts

@@ -739,10 +739,13 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
           .map((file) => path.basename(file))
           .join('|')
           .replace(/\./g, '\\.')
+        // require and import calls might be chained by minifier using the comma operator
+        // in this case we have to keep one comma
+        // if a next require is chained or add a semicolon to terminate the chain.
         const emptyChunkRE = new RegExp(
           opts.format === 'es'
-            ? `\\bimport\\s*["'][^"']*(?:${emptyChunkFiles})["'];\n?`
-            : `\\brequire\\(\\s*["'][^"']*(?:${emptyChunkFiles})["']\\);\n?`,
+            ? `(\\b|,\\s*)import\\s*["'][^"']*(?:${emptyChunkFiles})["'](;|,)`
+            : `(\\b|,\\s*)require\\(\\s*["'][^"']*(?:${emptyChunkFiles})["']\\)(;|,)`,
           'g',
         )
         for (const file in bundle) {
@@ -769,7 +772,7 @@ export function cssPostPlugin(config: ResolvedConfig): Plugin {
             chunk.code = chunk.code.replace(
               emptyChunkRE,
               // remove css import while preserving source map location
-              (m) => `/* empty css ${''.padEnd(m.length - 15)}*/`,
+              (m) => `/* empty css ${''.padEnd(m.length - 16)}*/${m.at(-1)}`,
             )
           }
         }