From 1b64e48ee1318804e22d5e7cafe4a8f493fd793e Mon Sep 17 00:00:00 2001
From: magic-akari <akari.ccino@gmail.com>
Date: Thu, 26 Oct 2023 11:07:30 +0800
Subject: [PATCH] feat(transformer): strip implicit type import for typescript
 (#1058)

---
 crates/oxc_transformer/src/lib.rs            |  3 +-
 crates/oxc_transformer/src/typescript/mod.rs | 69 +++++++++++++++++---
 tasks/transform_conformance/babel.snap.md    |  6 +-
 3 files changed, 63 insertions(+), 15 deletions(-)

diff --git a/crates/oxc_transformer/src/lib.rs b/crates/oxc_transformer/src/lib.rs
index 7cfa4506d..d78ad66dd 100644
--- a/crates/oxc_transformer/src/lib.rs
+++ b/crates/oxc_transformer/src/lib.rs
@@ -78,7 +78,8 @@ impl<'a> Transformer<'a> {
             scopes: Rc::clone(scopes),
         };
         Self {
-            typescript: source_type.is_typescript().then(|| TypeScript::new(Rc::clone(&ast))),
+            // TODO: pass verbatim_module_syntax from user config
+            typescript: source_type.is_typescript().then(|| TypeScript::new(Rc::clone(&ast), ctx.clone(), false)),
             react_jsx: options.react_jsx.map(|options| ReactJsx::new(Rc::clone(&ast), options)),
             regexp_flags: RegexpFlags::new(Rc::clone(&ast), &options),
             es2022_class_static_block: es2022::ClassStaticBlock::new(Rc::clone(&ast), &options),
diff --git a/crates/oxc_transformer/src/typescript/mod.rs b/crates/oxc_transformer/src/typescript/mod.rs
index bac896805..ef954cc84 100644
--- a/crates/oxc_transformer/src/typescript/mod.rs
+++ b/crates/oxc_transformer/src/typescript/mod.rs
@@ -1,20 +1,29 @@
 use oxc_ast::{ast::*, AstBuilder};
-use oxc_span::Span;
+use oxc_span::{Atom, Span};
 
 use std::rc::Rc;
 
+use crate::context::TransformerCtx;
+
 /// Transform TypeScript
 ///
 /// References:
 /// * <https://babeljs.io/docs/babel-plugin-transform-typescript>
 /// * <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-typescript>
+/// * <https://www.typescriptlang.org/tsconfig#verbatimModuleSyntax>
 pub struct TypeScript<'a> {
     ast: Rc<AstBuilder<'a>>,
+    ctx: TransformerCtx<'a>,
+    verbatim_module_syntax: bool,
 }
 
 impl<'a> TypeScript<'a> {
-    pub fn new(ast: Rc<AstBuilder<'a>>) -> Self {
-        Self { ast }
+    pub fn new(
+        ast: Rc<AstBuilder<'a>>,
+        ctx: TransformerCtx<'a>,
+        verbatim_module_syntax: bool,
+    ) -> Self {
+        Self { ast, ctx, verbatim_module_syntax }
     }
 
     #[allow(clippy::unused_self)]
@@ -37,13 +46,31 @@ impl<'a> TypeScript<'a> {
                     ModuleDeclaration::ExportNamedDeclaration(decl) => {
                         decl.specifiers.retain(|specifier| specifier.export_kind.is_value());
                     }
-                    ModuleDeclaration::ImportDeclaration(decl) => {
+                    ModuleDeclaration::ImportDeclaration(decl) if decl.import_kind.is_value() => {
                         if let Some(specifiers) = &mut decl.specifiers {
                             specifiers.retain(|specifier| match specifier {
                                 ImportDeclarationSpecifier::ImportSpecifier(s) => {
-                                    s.import_kind.is_value()
+                                    if s.import_kind.is_type() {
+                                        return false;
+                                    }
+
+                                    if self.verbatim_module_syntax {
+                                        return true;
+                                    }
+
+                                    self.has_value_references(&s.local.name)
                                 }
-                                _ => false,
+                                ImportDeclarationSpecifier::ImportDefaultSpecifier(s)
+                                    if !self.verbatim_module_syntax =>
+                                {
+                                    self.has_value_references(&s.local.name)
+                                }
+                                ImportDeclarationSpecifier::ImportNamespaceSpecifier(s)
+                                    if !self.verbatim_module_syntax =>
+                                {
+                                    self.has_value_references(&s.local.name)
+                                }
+                                _ => true,
                             });
                         }
                     }
@@ -58,19 +85,26 @@ impl<'a> TypeScript<'a> {
                     if decl.import_kind.is_type() {
                         return false;
                     }
-                    if decl.specifiers.as_ref().is_some_and(|specifiers| specifiers.is_empty()) {
-                        // TODO: verbatim_module_syntax
-                        return false;
+
+                    if self.verbatim_module_syntax {
+                        return true;
                     }
-                    true
+
+                    !decl.specifiers.as_ref().is_some_and(|specifiers| specifiers.is_empty())
                 }
                 ModuleDeclaration::ExportNamedDeclaration(decl) => {
                     if decl.export_kind.is_type() {
                         return false;
                     }
+
+                    if self.verbatim_module_syntax {
+                        return true;
+                    }
+
                     if decl.declaration.is_none() && decl.specifiers.is_empty() {
                         return false;
                     }
+
                     true
                 }
                 _ => true,
@@ -92,4 +126,19 @@ impl<'a> TypeScript<'a> {
             program.body.push(self.ast.module_declaration(export_decl));
         }
     }
+
+    fn has_value_references(&self, name: &Atom) -> bool {
+        let root_scope_id = self.ctx.scopes().root_scope_id();
+
+        self.ctx
+            .scopes()
+            .get_binding(root_scope_id, name)
+            .map(|symbol_id| {
+                self.ctx
+                    .symbols()
+                    .get_resolved_references(symbol_id)
+                    .any(|x| x.is_read() || x.is_write())
+            })
+            .unwrap_or_default()
+    }
 }
diff --git a/tasks/transform_conformance/babel.snap.md b/tasks/transform_conformance/babel.snap.md
index 2d66dddb9..1c0115594 100644
--- a/tasks/transform_conformance/babel.snap.md
+++ b/tasks/transform_conformance/babel.snap.md
@@ -1,4 +1,4 @@
-Passed: 173/1083
+Passed: 175/1083
 
 # All Passed:
 * babel-plugin-transform-numeric-separator
@@ -705,7 +705,7 @@ Passed: 173/1083
 * unicode-regex/negated-set/input.js
 * unicode-regex/slash/input.js
 
-# babel-plugin-transform-typescript (82/181)
+# babel-plugin-transform-typescript (84/181)
 * class/abstract-class-decorated/input.ts
 * class/abstract-class-decorated-method/input.ts
 * class/abstract-class-decorated-parameter/input.ts
@@ -752,9 +752,7 @@ Passed: 173/1083
 * imports/elide-no-import-specifiers/input.ts
 * imports/elide-preact/input.ts
 * imports/elide-type-referenced-in-imports-equal-no/input.ts
-* imports/elide-typeof/input.ts
 * imports/elision/input.ts
-* imports/elision-export-type/input.ts
 * imports/elision-locations/input.ts
 * imports/elision-rename/input.ts
 * imports/enum-id/input.ts