fix(transformer/typescript): remove type-only import = when `only_r…

…emove_type_imports` is true (#8275)

close: #8230
close: rolldown/rolldown#3287

Related PR in Babel: #8230

I have compared our output with TypeScript, and it is the same as `TypeScript`, Babel's implementation currently hasn't removed imports referenced by type-only `TSImportEqualsDeclaration`

crates/oxc_transformer/src/typescript/annotations.rs

@@ -143,9 +143,12 @@ impl<'a> Traverse<'a> for TypeScriptAnnotations<'a, '_> {
                         true
                     }
                 }
-                Statement::TSExportAssignment(_) | Statement::TSNamespaceExportDeclaration(_) => {
-                    false
-                }
+                // `import Binding = X.Y.Z`
+                // `Binding` can be referenced as a value or a type, but here we already know it only as a type
+                // See `TypeScriptModule::transform_ts_import_equals`
+                Statement::TSTypeAliasDeclaration(_)
+                | Statement::TSExportAssignment(_)
+                | Statement::TSNamespaceExportDeclaration(_) => false,
                 _ => return true,
             };
 

crates/oxc_transformer/src/typescript/mod.rs

@@ -57,7 +57,7 @@ impl<'a, 'ctx> TypeScript<'a, 'ctx> {
             annotations: TypeScriptAnnotations::new(options, ctx),
             r#enum: TypeScriptEnum::new(),
             namespace: TypeScriptNamespace::new(options, ctx),
-            module: TypeScriptModule::new(ctx),
+            module: TypeScriptModule::new(options.only_remove_type_imports, ctx),
             rewrite_extensions: TypeScriptRewriteExtensions::new(options),
         }
     }

crates/oxc_transformer/src/typescript/module.rs

@@ -1,4 +1,5 @@
 use oxc_ast::{ast::*, NONE};
+use oxc_semantic::Reference;
 use oxc_span::SPAN;
 use oxc_syntax::reference::ReferenceFlags;
 use oxc_traverse::{Traverse, TraverseCtx};
@@ -7,12 +8,14 @@ use super::diagnostics;
 use crate::TransformCtx;
 
 pub struct TypeScriptModule<'a, 'ctx> {
+    /// <https://babeljs.io/docs/babel-plugin-transform-typescript#onlyremovetypeimports>
+    only_remove_type_imports: bool,
     ctx: &'ctx TransformCtx<'a>,
 }
 
 impl<'a, 'ctx> TypeScriptModule<'a, 'ctx> {
-    pub fn new(ctx: &'ctx TransformCtx<'a>) -> Self {
-        Self { ctx }
+    pub fn new(only_remove_type_imports: bool, ctx: &'ctx TransformCtx<'a>) -> Self {
+        Self { only_remove_type_imports, ctx }
     }
 }
 
@@ -37,7 +40,9 @@ impl<'a> Traverse<'a> for TypeScriptModule<'a, '_> {
     fn enter_declaration(&mut self, decl: &mut Declaration<'a>, ctx: &mut TraverseCtx<'a>) {
         if let Declaration::TSImportEqualsDeclaration(import_equals) = decl {
             if import_equals.import_kind.is_value() {
-                *decl = self.transform_ts_import_equals(import_equals, ctx);
+                if let Some(new_decl) = self.transform_ts_import_equals(import_equals, ctx) {
+                    *decl = new_decl;
+                }
             }
         }
     }
@@ -88,7 +93,29 @@ impl<'a> TypeScriptModule<'a, '_> {
         &self,
         decl: &mut TSImportEqualsDeclaration<'a>,
         ctx: &mut TraverseCtx<'a>,
-    ) -> Declaration<'a> {
+    ) -> Option<Declaration<'a>> {
+        if !self.only_remove_type_imports
+            && !ctx.parent().is_export_named_declaration()
+            && ctx.symbols().get_resolved_references(decl.id.symbol_id()).all(Reference::is_type)
+        {
+            // No value reference, we will remove this declaration in `TypeScriptAnnotations`
+            match &mut decl.module_reference {
+                module_reference @ match_ts_type_name!(TSModuleReference) => {
+                    let ident = module_reference.to_ts_type_name().get_identifier_reference();
+                    let reference = ctx.symbols_mut().get_reference_mut(ident.reference_id());
+                    // The binding of TSImportEqualsDeclaration has treated as a type reference,
+                    // so an identifier reference that it referenced also should be treated as a type reference.
+                    // `import TypeBinding = X.Y.Z`
+                    //                       ^ `X` should be treated as a type reference.
+                    let flags = reference.flags_mut();
+                    debug_assert_eq!(*flags, ReferenceFlags::Read);
+                    *flags = ReferenceFlags::Type;
+                }
+                TSModuleReference::ExternalModuleReference(_) => {}
+            }
+            return None;
+        }
+
         let binding_pattern_kind =
             ctx.ast.binding_pattern_kind_binding_identifier(SPAN, &decl.id.name);
         let binding = ctx.ast.binding_pattern(binding_pattern_kind, NONE, false);
@@ -123,7 +150,7 @@ impl<'a> TypeScriptModule<'a, '_> {
         let decls =
             ctx.ast.vec1(ctx.ast.variable_declarator(SPAN, kind, binding, Some(init), false));
 
-        ctx.ast.declaration_variable(SPAN, kind, decls, false)
+        Some(ctx.ast.declaration_variable(SPAN, kind, decls, false))
     }
 
     #[allow(clippy::only_used_in_recursion)]

napi/transform/test/transform.test.ts

@@ -138,13 +138,19 @@ describe('modules', () => {
     const code = `
 export = function foo (): void {}
 import bar = require('bar')
+console.log(bar)
 `;
     const ret = transform('test.ts', code, {
       typescript: {
         declaration: {},
       },
     });
-    expect(ret.code).toEqual('module.exports = function foo() {};\nconst bar = require("bar");\n');
+    expect(ret.code).toMatchInlineSnapshot(`
+      "module.exports = function foo() {};
+      const bar = require("bar");
+      console.log(bar);
+      "
+    `);
     expect(ret.declaration).toEqual('declare const _default: () => void;\nexport = _default;\n');
   });
 });

tasks/coverage/snapshots/semantic_babel.snap

@@ -130,10 +130,9 @@ after transform: ["Y", "foo"]
 rebuilt        : []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/estree/typescript/import-require/input.js
-semantic error: Missing SymbolId: "x"
-Binding symbols mismatch:
-after transform: ScopeId(0): [SymbolId(0)]
-rebuilt        : ScopeId(0): [SymbolId(0)]
+semantic error: Bindings mismatch:
+after transform: ScopeId(0): ["x"]
+rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/estree/typescript/literals/input.js
 semantic error: Scope children mismatch:
@@ -723,28 +722,30 @@ after transform: ScopeId(0): [ScopeId(1), ScopeId(2)]
 rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/equals/input.ts
-semantic error: Missing SymbolId: "A"
-Binding symbols mismatch:
-after transform: ScopeId(0): [SymbolId(0)]
-rebuilt        : ScopeId(0): [SymbolId(0)]
+semantic error: Bindings mismatch:
+after transform: ScopeId(0): ["A"]
+rebuilt        : ScopeId(0): []
+Unresolved references mismatch:
+after transform: ["B"]
+rebuilt        : []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/equals-in-unambiguous/input.ts
-semantic error: Missing SymbolId: "A"
-Binding symbols mismatch:
-after transform: ScopeId(0): [SymbolId(0)]
-rebuilt        : ScopeId(0): [SymbolId(0)]
+semantic error: Bindings mismatch:
+after transform: ScopeId(0): ["A"]
+rebuilt        : ScopeId(0): []
+Unresolved references mismatch:
+after transform: ["B"]
+rebuilt        : []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/equals-require/input.ts
-semantic error: Missing SymbolId: "a"
-Binding symbols mismatch:
-after transform: ScopeId(0): [SymbolId(0)]
-rebuilt        : ScopeId(0): [SymbolId(0)]
+semantic error: Bindings mismatch:
+after transform: ScopeId(0): ["a"]
+rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/equals-require-in-unambiguous/input.ts
-semantic error: Missing SymbolId: "a"
-Binding symbols mismatch:
-after transform: ScopeId(0): [SymbolId(0)]
-rebuilt        : ScopeId(0): [SymbolId(0)]
+semantic error: Bindings mismatch:
+after transform: ScopeId(0): ["a"]
+rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/export-import/input.ts
 semantic error: Missing SymbolId: "A"
@@ -799,10 +800,9 @@ after transform: ScopeId(0): ["a"]
 rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/import-type-as-identifier/input.ts
-semantic error: Missing SymbolId: "type"
-Binding symbols mismatch:
-after transform: ScopeId(0): [SymbolId(0)]
-rebuilt        : ScopeId(0): [SymbolId(0)]
+semantic error: Bindings mismatch:
+after transform: ScopeId(0): ["type"]
+rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/import/internal-comments/input.ts
 semantic error: Bindings mismatch:
@@ -1431,8 +1431,7 @@ after transform: ScopeId(0): [ScopeId(1)]
 rebuilt        : ScopeId(0): []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/scope/redeclaration-import-equals-var/input.ts
-semantic error: Missing SymbolId: "a"
-Bindings mismatch:
+semantic error: Bindings mismatch:
 after transform: ScopeId(0): ["M", "a"]
 rebuilt        : ScopeId(0): ["a"]
 Scope children mismatch:
@@ -1443,7 +1442,13 @@ after transform: SymbolId(1): SymbolFlags(FunctionScopedVariable | Import)
 rebuilt        : SymbolId(0): SymbolFlags(FunctionScopedVariable)
 Symbol span mismatch for "a":
 after transform: SymbolId(1): Span { start: 20, end: 21 }
-rebuilt        : SymbolId(0): Span { start: 0, end: 0 }
+rebuilt        : SymbolId(0): Span { start: 31, end: 32 }
+Symbol redeclarations mismatch for "a":
+after transform: SymbolId(1): [Span { start: 31, end: 32 }]
+rebuilt        : SymbolId(0): []
+Unresolved references mismatch:
+after transform: ["M"]
+rebuilt        : []
 
 tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/scope/redeclaration-import-let/input.ts
 semantic error: Symbol flags mismatch for "Context":