don't emit "unused @ts-expect-error" in unchecked js files (#40046)

* don't emit unused ts-expect-error in unchecked js files

* simplify code

src/compiler/program.ts

@@ -1747,13 +1747,13 @@ namespace ts {
                 const bindDiagnostics: readonly Diagnostic[] = includeBindAndCheckDiagnostics ? sourceFile.bindDiagnostics : emptyArray;
                 const checkDiagnostics = includeBindAndCheckDiagnostics ? typeChecker.getDiagnostics(sourceFile, cancellationToken) : emptyArray;
 
-                return getMergedBindAndCheckDiagnostics(sourceFile, bindDiagnostics, checkDiagnostics, isCheckJs ? sourceFile.jsDocDiagnostics : undefined);
+                return getMergedBindAndCheckDiagnostics(sourceFile, includeBindAndCheckDiagnostics, bindDiagnostics, checkDiagnostics, isCheckJs ? sourceFile.jsDocDiagnostics : undefined);
             });
         }
 
-        function getMergedBindAndCheckDiagnostics(sourceFile: SourceFile, ...allDiagnostics: (readonly Diagnostic[] | undefined)[]) {
+        function getMergedBindAndCheckDiagnostics(sourceFile: SourceFile, includeBindAndCheckDiagnostics: boolean, ...allDiagnostics: (readonly Diagnostic[] | undefined)[]) {
             const flatDiagnostics = flatten(allDiagnostics);
-            if (!sourceFile.commentDirectives?.length) {
+            if (!includeBindAndCheckDiagnostics || !sourceFile.commentDirectives?.length) {
                 return flatDiagnostics;
             }
 

tests/baselines/reference/ts-expect-error-js.errors.txt

@@ -0,0 +1,11 @@
+tests/cases/conformance/directives/a.js(3,1): error TS2578: Unused '@ts-expect-error' directive.
+
+
+==== tests/cases/conformance/directives/a.js (1 errors) ====
+    // there should be a "Unused @ts-expect-error" error since js files are being checked
+    
+    // @ts-expect-error
+    ~~~~~~~~~~~~~~~~~~~
+!!! error TS2578: Unused '@ts-expect-error' directive.
+    const a = 1;
+    

tests/baselines/reference/ts-expect-error-js.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/conformance/directives/a.js ===
+// there should be a "Unused @ts-expect-error" error since js files are being checked
+
+// @ts-expect-error
+const a = 1;
+>a : Symbol(a, Decl(a.js, 3, 5))
+

tests/baselines/reference/ts-expect-error-js.types

@@ -0,0 +1,8 @@
+=== tests/cases/conformance/directives/a.js ===
+// there should be a "Unused @ts-expect-error" error since js files are being checked
+
+// @ts-expect-error
+const a = 1;
+>a : 1
+>1 : 1
+

tests/baselines/reference/ts-expect-error-nocheck-js.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/conformance/directives/a.js ===
+// there should not be a "Unused @ts-expect-error" error since js files are not being checked
+
+// @ts-expect-error
+const a = 1;
+>a : Symbol(a, Decl(a.js, 3, 5))
+

tests/baselines/reference/ts-expect-error-nocheck-js.types

@@ -0,0 +1,8 @@
+=== tests/cases/conformance/directives/a.js ===
+// there should not be a "Unused @ts-expect-error" error since js files are not being checked
+
+// @ts-expect-error
+const a = 1;
+>a : 1
+>1 : 1
+

tests/baselines/reference/ts-expect-error-nocheck.js

@@ -0,0 +1,14 @@
+//// [ts-expect-error-nocheck.ts]
+// @ts-nocheck
+
+// there should not be a "Unused @ts-expect-error" error due to the // @ts-nocheck
+
+// @ts-expect-error
+const a = 1;
+
+
+//// [ts-expect-error-nocheck.js]
+// @ts-nocheck
+// there should not be a "Unused @ts-expect-error" error due to the // @ts-nocheck
+// @ts-expect-error
+var a = 1;

tests/baselines/reference/ts-expect-error-nocheck.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/conformance/directives/ts-expect-error-nocheck.ts ===
+// @ts-nocheck
+
+// there should not be a "Unused @ts-expect-error" error due to the // @ts-nocheck
+
+// @ts-expect-error
+const a = 1;
+>a : Symbol(a, Decl(ts-expect-error-nocheck.ts, 5, 5))
+

tests/baselines/reference/ts-expect-error-nocheck.types

@@ -0,0 +1,10 @@
+=== tests/cases/conformance/directives/ts-expect-error-nocheck.ts ===
+// @ts-nocheck
+
+// there should not be a "Unused @ts-expect-error" error due to the // @ts-nocheck
+
+// @ts-expect-error
+const a = 1;
+>a : 1
+>1 : 1
+

tests/cases/conformance/directives/ts-expect-error-js.ts

@@ -0,0 +1,10 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+
+// @fileName: a.js
+
+// there should be a "Unused @ts-expect-error" error since js files are being checked
+
+// @ts-expect-error
+const a = 1;

tests/cases/conformance/directives/ts-expect-error-nocheck-js.ts

@@ -0,0 +1,10 @@
+// @allowJs: true
+// @checkJs: false
+// @noEmit: true
+
+// @fileName: a.js
+
+// there should not be a "Unused @ts-expect-error" error since js files are not being checked
+
+// @ts-expect-error
+const a = 1;

tests/cases/conformance/directives/ts-expect-error-nocheck.ts

@@ -0,0 +1,6 @@
+// @ts-nocheck
+
+// there should not be a "Unused @ts-expect-error" error due to the // @ts-nocheck
+
+// @ts-expect-error
+const a = 1;