feat(coverage): second transformer build does not print typescript (#3561)

Currently, we lack a test to check if the TS AST has been completely deleted. I have thought of a way to test it. Let's have our idempotency test print the TypeScript code the first time and the second time print the JavaScript code only. If the two results do not match, it means that there are still undeleted TS ASTs or other bugs. Since ideally the TS ASTs are completely deleted, the two results should be the same.

crates/oxc_codegen/src/gen.rs

@@ -2405,8 +2405,7 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for MethodDefinition<'a> {
         }
         if let Some(body) = &self.value.body {
             body.gen(p, ctx);
-        }
-        if p.options.enable_typescript {
+        } else if p.options.enable_typescript {
             p.print_semicolon_after_statement();
         }
     }

tasks/coverage/src/transformer.rs

@@ -43,7 +43,7 @@ fn get_result(
     let options = options.unwrap_or_else(get_default_transformer_options);
     let parse_result1 = Parser::new(&allocator, source_text, source_type).parse();
     let mut program = parse_result1.program;
-    let _ = Transformer::new(
+    let transform_result1 = Transformer::new(
         &allocator,
         source_path,
         source_type,
@@ -53,7 +53,7 @@ fn get_result(
     )
     .build(&mut program);
 
-    let source_text1 = Codegen::<false>::new(
+    let ts_source_text1 = Codegen::<false>::new(
         &filename,
         source_text,
         CodegenOptions::default().with_typescript(true),
@@ -62,10 +62,19 @@ fn get_result(
     .build(&program)
     .source_text;
 
-    let parse_result2 = Parser::new(&allocator, &source_text1, source_type).parse();
+    let source_text1 =
+        Codegen::<false>::new(&filename, source_text, CodegenOptions::default(), None)
+            .build(&program)
+            .source_text;
+
+    if transform_result1.is_ok() && ts_source_text1 != source_text1 {
+        return TestResult::Mismatch(ts_source_text1.clone(), source_text1.clone());
+    }
+
+    let parse_result2 = Parser::new(&allocator, &ts_source_text1, source_type).parse();
     let mut program = parse_result2.program;
 
-    let _ = Transformer::new(
+    let transform_result2 = Transformer::new(
         &allocator,
         source_path,
         source_type,
@@ -75,19 +84,22 @@ fn get_result(
     )
     .build(&mut program);
 
-    let source_text2 = Codegen::<false>::new(
-        &filename,
-        &source_text1,
-        CodegenOptions::default().with_typescript(true),
-        None,
-    )
-    .build(&program)
-    .source_text;
+    let source_text2 =
+        Codegen::<false>::new(&filename, &source_text1, CodegenOptions::default(), None)
+            .build(&program)
+            .source_text;
 
-    let result = source_text1 == source_text2;
-
-    if result {
+    if source_text1 == source_text2 {
         TestResult::Passed
+    } else if transform_result1.is_err_and(|err| {
+        // If error messages are the same, we consider it as a pass.
+        transform_result2
+            .map_err(|err| err.iter().map(ToString::to_string).collect::<Vec<_>>().join("\n"))
+            .is_err_and(|err_message| {
+                err.iter().map(ToString::to_string).collect::<Vec<_>>().join("\n") == err_message
+            })
+    }) {
+        return TestResult::Passed;
     } else {
         TestResult::Mismatch(source_text1.clone(), source_text2)
     }

tasks/coverage/transformer_babel.snap

@@ -2,4 +2,6 @@ commit: 4bd1b2c2
 
 transformer_babel Summary:
 AST Parsed     : 2099/2099 (100.00%)
-Positive Passed: 2099/2099 (100.00%)
+Positive Passed: 2097/2099 (99.90%)
+Mismatch: "typescript/class/parameter-properties/input.ts"
+Mismatch: "typescript/export/as-namespace/input.ts"

tasks/coverage/transformer_typescript.snap

@@ -2,5 +2,37 @@ commit: 64d2eeea
 
 transformer_typescript Summary:
 AST Parsed     : 5243/5243 (100.00%)
-Positive Passed: 5242/5243 (99.98%)
+Positive Passed: 5210/5243 (99.37%)
+Mismatch: "compiler/amdModuleName1.ts"
+Mismatch: "compiler/avoidCycleWithVoidExpressionReturnedFromArrow.ts"
+Mismatch: "compiler/clinterfaces.ts"
+Mismatch: "compiler/collectionPatternNoError.ts"
+Mismatch: "compiler/comparabilityTypeParametersRelatedByUnion.ts"
+Mismatch: "compiler/constEnumMergingWithValues1.ts"
+Mismatch: "compiler/constEnumMergingWithValues2.ts"
+Mismatch: "compiler/constEnumMergingWithValues3.ts"
+Mismatch: "compiler/constEnumMergingWithValues4.ts"
+Mismatch: "compiler/constEnumMergingWithValues5.ts"
 Mismatch: "compiler/elidedEmbeddedStatementsReplacedWithSemicolon.ts"
+Mismatch: "compiler/es5-umd4.ts"
+Mismatch: "compiler/exportAssignValueAndType.ts"
+Mismatch: "compiler/exportAssignmentWithPrivacyError.ts"
+Mismatch: "compiler/exportAssignmentWithoutIdentifier1.ts"
+Mismatch: "compiler/exportEqualNamespaces.ts"
+Mismatch: "compiler/exportEqualsAmd.ts"
+Mismatch: "compiler/exportEqualsClassNoRedeclarationError.ts"
+Mismatch: "compiler/exportEqualsCommonJs.ts"
+Mismatch: "compiler/exportEqualsUmd.ts"
+Mismatch: "compiler/module_augmentUninstantiatedModule2.ts"
+Mismatch: "compiler/noCircularDefinitionOnExportOfPrivateInMergedNamespace.ts"
+Mismatch: "compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.ts"
+Mismatch: "compiler/recursiveFieldSetting.ts"
+Mismatch: "compiler/sourceMapValidationExportAssignment.ts"
+Mismatch: "compiler/sourceMapValidationExportAssignmentCommonjs.ts"
+Mismatch: "compiler/varianceProblingAndZeroOrderIndexSignatureRelationsAlign.ts"
+Mismatch: "compiler/varianceProblingAndZeroOrderIndexSignatureRelationsAlign2.ts"
+Mismatch: "conformance/classes/members/privateNames/privateNameFieldParenthesisLeftAssignment.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/initializationOrdering1.ts"
+Mismatch: "conformance/classes/propertyMemberDeclarations/instanceMemberInitialization.ts"
+Mismatch: "conformance/decorators/class/constructor/parameter/decoratorOnClassConstructorParameter5.ts"
+Mismatch: "conformance/statements/VariableStatements/usingDeclarations/usingDeclarationsTopLevelOfModule.2.ts"