fix(build): add --ignoreConfig for TypeScript 7 to prevent TS5112

integration-tests/typescript-versions.test.js

@@ -115,6 +115,29 @@ describe.each(TS_VERSIONS)('with typescript@%s', (version) => {
     INSTALL_AND_BUILD_TIMEOUT,
   );
 
+  it(
+    'should build a .ts file when tsconfig.json is present in the CWD but no --tsconfig flag is passed (TS5112 regression)',
+    async () => {
+      // TS 7 errors with TS5112 when a file is passed on the CLI and an ambient
+      // tsconfig.json exists in the CWD. --ignoreConfig suppresses it; this test
+      // locks the exact invocation so the flag cannot be silently dropped.
+      expect.assertions(2);
+      const { execute, cleanup, writeFile } = await setup();
+      await writeFile('input.ts', VALID_TS);
+      await writeFile('tsconfig.json', JSON.stringify({ compilerOptions: { strict: true } }));
+
+      const { code, stdout } = await execute(
+        'node',
+        './bin/fastedge-build.js input.ts dist/output.wasm',
+      );
+
+      expect(code).toBe(0);
+      expect(stdout[0]).toContain('Build success!!');
+      await cleanup();
+    },
+    INSTALL_AND_BUILD_TIMEOUT,
+  );
+
   it(
     'should reject a TypeScript entrypoint with a type error',
     async () => {

src/utils/syntax-checker.ts

@@ -127,6 +127,12 @@ function containsTypeScriptSyntaxErrors(tsInput: string, tsConfigPath?: string):
   // TS infers from `--target esnext` is es2015, which rejects `import.meta`
   // with TS1343 even though it is valid ESM that the runtime supports.
   // `esnext` matches how input is actually consumed: esbuild bundles ESM.
+
+  // TS 6+ errors with TS5112 when a file is passed on the command line and a
+  // tsconfig.json exists in the CWD. We control all flags explicitly here, so
+  // ignoring any ambient tsconfig is correct.
+  const ignoreConfig = typescript.major >= 6 ? ['--ignoreConfig'] : [];
+
   const defaultTscBuildFlags = [
     '--noEmit',
     '--skipLibCheck',
@@ -138,6 +144,7 @@ function containsTypeScriptSyntaxErrors(tsInput: string, tsConfigPath?: string):
     'esnext',
     '--moduleResolution',
     moduleResolution,
+    ...ignoreConfig,
     ...includeFastEdgeTypes,
     tsInput,
   ];