fix(wasm): test glue literals for a .wasm suffix in linear time (#6237)

associateWasmGlue tested every glue string literal with
/\.wasm(?:[?#].*)?$/iu. Each .wasm? or .wasm# occurrence scanned to the
next line terminator and failed at $, so a multi-line literal with many
such occurrences took quadratic time on the event loop (about 2.6 s for
192 KB, within the 8 MiB glue limit). Because . cannot cross a line
terminator and $ only matches at the end, test the literal's last line
only; results are unchanged.

src/wasm/WabtOutput.test.ts

@@ -381,3 +381,16 @@ it("matches a CLI-selected ./ module exactly against its glue reference", () =>
     },
   ]);
 });
+
+it("tests long multi-line glue literals for a .wasm suffix in linear time", () => {
+  const value = `${".wasm#".repeat(32_000)}\nend`;
+  const started = performance.now();
+  expect(
+    associateWasmGlue(`const s = ${JSON.stringify(value)};`, "/glue.js", []),
+  ).toEqual({ parse_status: "complete", references: [] });
+  expect(performance.now() - started).toBeLessThan(1_000);
+  expect(
+    associateWasmGlue("const s = `first\nmodule.wasm?v=1`;", "/glue.js", [])
+      .references,
+  ).toMatchObject([{ value: "first\nmodule.wasm?v=1", line: 1 }]);
+});

src/wasm/WasmGlueAdapter.ts

@@ -3,6 +3,24 @@ import * as t from "@babel/types";
 import { parseJavaScriptSource } from "../domain/javascript/javascriptSourceParser.js";
 import { traverseJavaScriptAst } from "../domain/javascript/javascriptSemanticTraversal.js";
 import { absoluteCallerPath } from "../filesystem/callerPath.js";
+
+/**
+ * `.` cannot cross a line terminator and `$` only matches at the end of the
+ * literal, so a `.wasm` suffix can only occur on its last line. Testing that
+ * line alone keeps long multi-line literals linear.
+ */
+const endsWithWasmReference = (value: string): boolean =>
+  /\.wasm(?:[?#].*)?$/iu.test(
+    value.slice(
+      Math.max(
+        value.lastIndexOf("\n"),
+        value.lastIndexOf("\r"),
+        value.lastIndexOf("
"),
+        value.lastIndexOf("
"),
+      ) + 1,
+    ),
+  );
+
 /** Associate visible literals with selected candidates without asserting data flow or URL identity. */
 export const associateWasmGlue = (
   source: string,
@@ -43,7 +61,7 @@ export const associateWasmGlue = (
       if (
         value === undefined ||
         value === null ||
-        !/\.wasm(?:[?#].*)?$/iu.test(value) ||
+        !endsWithWasmReference(value) ||
         node.loc == null
       )
         return;