feat: add DTS resolver matching TypeScript's bundler mode by Boshen · Pull Request #997 · oxc-project/oxc-resolver

Boshen · 2026-02-06T06:27:23Z

Summary

Add resolve_dts() method to ResolverGeneric implementing TypeScript's ts.resolveModuleName with moduleResolution: "bundler" algorithm
Two-pass node_modules walk: all ancestors for TS/DTS + @types before trying JS — fixes the fundamental algorithmic difference that JS workarounds can't address
@types scoped name mangling (@babel/core → @types/babel__core)
TypeScript extension substitution (.js → .ts, .d.ts) following TS priority order
typesVersions package.json field support
exports field absolute priority (blocks types/typings/main when present)
NAPI bindings: resolveDtsSync / resolveDtsAsync
20 test cases covering relative resolution, extension substitution/priority, directory modules, @types, exports, typesVersions, typings field, and name mangling

Closes #549

🤖 Generated with Claude Code

…ler"` Add `resolve_dts()` method to `ResolverGeneric` that implements TypeScript's `ts.resolveModuleName` algorithm for declaration file resolution. This replaces the need for JS workarounds that configure enhanced-resolve with DTS-friendly options but can't match TypeScript's actual resolution behavior. Key features: - Two-pass node_modules walk: TS/DTS + @types before JS - @types scoped name mangling (@babel/core -> @types/babel__core) - TypeScript extension substitution (.js -> .ts, .d.ts) - typesVersions package.json field support - exports field absolute priority (blocks types/typings/main) - NAPI bindings: resolveDtsSync / resolveDtsAsync Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

codecov · 2026-02-06T06:28:34Z

Codecov Report

❌ Patch coverage is 75.18797% with 132 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.62%. Comparing base (a644254) to head (9e682ba).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/dts_resolver.rs	74.11%	132 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #997      +/-   ##
==========================================
- Coverage   94.02%   91.62%   -2.41%     
==========================================
  Files          17       18       +1     
  Lines        3348     3880     +532     
==========================================
+ Hits         3148     3555     +407     
- Misses        200      325     +125

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codspeed-hq · 2026-02-06T06:36:36Z

Merging this PR will not alter performance

✅ 12 untouched benchmarks
⏩ 5 skipped benchmarks¹

_{Comparing feat/dts-resolver (9e682ba) with main (42b7ef4)}

5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Copilot

Pull request overview

This PR adds a DTS resolver that implements TypeScript's ts.resolveModuleName with moduleResolution: "bundler" algorithm. The implementation addresses a critical gap for tools like rolldown-plugin-dts that need to inline and bundle type declarations, and solves numerous edge cases that cannot be handled by workarounds using the existing JavaScript resolver.

Changes:

Implements a new resolve_dts() method with TypeScript-specific resolution logic including two-pass node_modules walk, @types scoped name mangling, TypeScript extension substitution, typesVersions support, and proper exports field handling
Adds package.json field accessors for types, typings, and typesVersions fields in both simd and serde implementations
Exposes resolveDtsSync and resolveDtsAsync methods through NAPI bindings with comprehensive documentation

Reviewed changes

Copilot reviewed 18 out of 41 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/dts_resolver.rs	Core DTS resolution algorithm implementation with TypeScript-specific logic
src/tests/dts_resolver.rs	Comprehensive test suite with 20 test cases covering relative resolution, extension priority, @types, exports, typesVersions, and name mangling
src/package_json/simd.rs	Added types(), typings(), and types_versions() accessors for SIMD JSON parser
src/package_json/serde.rs	Added types(), typings(), and types_versions() accessors for serde JSON parser
napi/src/lib.rs	NAPI bindings for resolve_dts_sync and resolve_dts_async
napi/index.d.ts	TypeScript type definitions for DTS resolution methods
src/tests/mod.rs	Added dts_resolver test module
src/lib.rs	Added dts_resolver module
fixtures/dts_resolver/*	Test fixtures for DTS resolution scenarios

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Copilot · 2026-02-06T09:47:03Z

src/dts_resolver.rs

+    /// `specifier` is the module specifier string.
+    ///
+    /// The resolver uses the existing `ResolveOptions` for:
+    /// - `condition_names` (used for `exports` resolution; `"types"` is always added)


The documentation states that "types" is always added to condition_names, but this is not implemented in the code. Users must manually include "types" in their ResolveOptions.condition_names (as shown in the test at src/tests/dts_resolver.rs:13). Either update the documentation to reflect the actual behavior, or implement the automatic addition of "types" to condition_names when calling resolve_dts.

Copilot · 2026-02-06T09:47:04Z

src/dts_resolver.rs

+            let mut entry = if extensions.contains(Extensions::DECLARATION) {
+                pkg.typings().or_else(|| pkg.types())
+            } else {
+                None
+            };
+            if entry.is_none()
+                && extensions.intersects(
+                    Extensions::TYPESCRIPT
+                        .union(Extensions::JAVASCRIPT)
+                        .union(Extensions::DECLARATION),
+                )
+            {
+                entry = pkg.main_fields(&main_fields).next();
+            }
+
+            let vp_specifier = entry.unwrap_or("index");
+            if let Some(path) = self.dts_resolve_via_version_paths(
+                extensions,
+                vp_specifier,
+                candidate,
+                &version_paths,
+                ctx,
+            )? {
+                return Ok(Some(path));
+            }
+        }
+
+        // Determine entry file (types/typings/main)
+        if let Some(ref pkg) = pkg {
+            let mut entry = if extensions.contains(Extensions::DECLARATION) {
+                pkg.typings().or_else(|| pkg.types())
+            } else {
+                None
+            };
+            if entry.is_none()
+                && extensions.intersects(
+                    Extensions::TYPESCRIPT
+                        .union(Extensions::JAVASCRIPT)
+                        .union(Extensions::DECLARATION),
+                )
+            {
+                entry = pkg.main_fields(&main_fields).next();
+            }


There is duplicate logic for determining the entry field (types/typings/main). Lines 390-403 and 419-432 contain nearly identical code. Consider extracting this into a helper method to reduce duplication and improve maintainability.

Copilot · 2026-02-06T09:47:04Z

src/dts_resolver.rs

+            }
+            _ => {
+                // Unknown extensions like .vue, .svelte - return them for d.{ext}.ts handling
+                if !ext.is_empty() && ext.len() < 10 { Some(ext) } else { None }


Consider extracting the magic number 10 to a named constant like MAX_UNKNOWN_EXTENSION_LENGTH to improve code readability and make the intent clearer.

Boshen requested a review from Copilot February 6, 2026 09:42

Boshen marked this pull request as ready for review February 6, 2026 09:42

Copilot started reviewing on behalf of Boshen February 6, 2026 09:42 View session

Copilot AI reviewed Feb 6, 2026

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Boshen self-assigned this Feb 6, 2026

camc314 mentioned this pull request Feb 9, 2026

feat(linter): Add eslint/no-unresolved rule oxc-project/oxc#18044

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feat: add DTS resolver matching TypeScript's bundler mode#997

feat: add DTS resolver matching TypeScript's bundler mode#997
Boshen wants to merge 1 commit intomainfrom
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Boshen commented Feb 6, 2026

Summary

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codspeed-hq bot commented Feb 6, 2026

Merging this PR will not alter performance

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