Implement external package stub mode with persistent stubs

- Changed stub generation directory from vendor/ to external_stubs/ to avoid Go vendor conflicts
- Modified stub generator to not overwrite existing stub implementations
- Added test configuration support via .go2rust.toml files
- Updated test script to read config and pass --external-packages flag
- Implemented working decimal stub for external_simple test
- Test auto-promoted from XFAIL to passing

The stub mode now properly:
1. Generates stub files in external_stubs/ directory on first run
2. Preserves manual stub implementations on subsequent runs
3. Allows tests to specify their external package strategy via config file

Signed-off-by: Tyler Laprade <[email protected]>

Author: tylerlaprade

go/external_packages.go

@@ -108,15 +108,15 @@ func (h *ExternalPackageHandler) updateCargoWorkspace() error {
 	// Add external packages as workspace members
 	for pkg := range h.packageMapping {
 		crateName := h.packageMapping[pkg]
-		workspaceSection += fmt.Sprintf("    \"vendor/%s\",\n", crateName)
+		workspaceSection += fmt.Sprintf("    \"external_stubs/%s\",\n", crateName)
 	}
 	workspaceSection += "]\n\n"
 
 	// Add dependencies section for external packages
 	depsSection := "[dependencies]\n"
 	for pkg := range h.packageMapping {
 		crateName := h.packageMapping[pkg]
-		depsSection += fmt.Sprintf("%s = { path = \"vendor/%s\" }\n", crateName, crateName)
+		depsSection += fmt.Sprintf("%s = { path = \"external_stubs/%s\" }\n", crateName, crateName)
 	}
 
 	// Combine workspace section with existing package configuration

go/project.go

@@ -179,7 +179,7 @@ func (pg *ProjectGenerator) generateInternal(skipExternalHandling bool) error {
 		if err != nil {
 			// This is expected with stubs - external types won't be available
 			fmt.Fprintf(os.Stderr, "Note: Type checking incomplete (external packages are stubs): %v\n", err)
-			fmt.Fprintf(os.Stderr, "You will need to implement the stub packages in vendor/\n")
+			fmt.Fprintf(os.Stderr, "You will need to implement the stub packages in external_stubs/\n")
 		}
 		pg.typeInfo = typeInfo
 		SetTypeInfo(typeInfo)
@@ -440,7 +440,7 @@ path = "main.rs"
 	if len(pg.packageMapping) > 0 {
 		workspaceSection := "\n[workspace]\nmembers = [\n    \".\",\n"
 		for _, crateName := range pg.packageMapping {
-			workspaceSection += fmt.Sprintf("    \"vendor/%s\",\n", crateName)
+			workspaceSection += fmt.Sprintf("    \"external_stubs/%s\",\n", crateName)
 		}
 		workspaceSection += "]\n"
 		cargoContent = workspaceSection + "\n" + cargoContent
@@ -454,7 +454,7 @@ path = "main.rs"
 		}
 		// Add external package dependencies
 		for _, crateName := range pg.packageMapping {
-			cargoContent += fmt.Sprintf("%s = { path = \"vendor/%s\" }\n", crateName, crateName)
+			cargoContent += fmt.Sprintf("%s = { path = \"external_stubs/%s\" }\n", crateName, crateName)
 		}
 	}
 

go/stub_generator.go

@@ -71,10 +71,10 @@ func (sg *StubGenerator) generateStub(importPath, pkgName string) error {
 	crateName := sg.goPathToRustCrate(importPath)
 	sg.packageMapping[importPath] = crateName
 
-	// Create vendor directory
-	vendorDir := filepath.Join(sg.projectPath, "vendor")
+	// Create external_stubs directory
+	vendorDir := filepath.Join(sg.projectPath, "external_stubs")
 	if err := os.MkdirAll(vendorDir, 0755); err != nil {
-		return fmt.Errorf("failed to create vendor directory: %v", err)
+		return fmt.Errorf("failed to create external_stubs directory: %v", err)
 	}
 
 	// Create package directory
@@ -83,11 +83,16 @@ func (sg *StubGenerator) generateStub(importPath, pkgName string) error {
 		return fmt.Errorf("failed to create package directory: %v", err)
 	}
 
-	// Generate lib.rs with TODO comments
+	// Generate lib.rs with TODO comments (only if it doesn't exist)
 	libRsPath := filepath.Join(pkgDir, "lib.rs")
-	libRsContent := sg.generateLibRsContent(importPath, pkgName)
-	if err := os.WriteFile(libRsPath, []byte(libRsContent), 0644); err != nil {
-		return fmt.Errorf("failed to write lib.rs: %v", err)
+	if _, err := os.Stat(libRsPath); os.IsNotExist(err) {
+		libRsContent := sg.generateLibRsContent(importPath, pkgName)
+		if err := os.WriteFile(libRsPath, []byte(libRsContent), 0644); err != nil {
+			return fmt.Errorf("failed to write lib.rs: %v", err)
+		}
+		fmt.Fprintf(os.Stderr, "Generated NEW stub for %s at external_stubs/%s/\n", importPath, crateName)
+	} else {
+		fmt.Fprintf(os.Stderr, "Using existing stub for %s at external_stubs/%s/\n", importPath, crateName)
 	}
 
 	// Generate Cargo.toml
@@ -110,7 +115,6 @@ path = "lib.rs"
 	}
 
 	sg.generatedStubs[importPath] = true
-	fmt.Fprintf(os.Stderr, "Generated stub for %s at vendor/%s/\n", importPath, crateName)
 	return nil
 }
 

tests.bats

@@ -78,8 +78,22 @@ run_transpile_and_compare() {
     local test_dir="$1"
     local go_output="$2"
 
+    # Check for test-specific configuration
+    local external_mode=""
+    if [ -f "$test_dir/.go2rust.toml" ]; then
+        # Simple parsing - just look for external_packages line
+        external_mode=$(grep "^external_packages" "$test_dir/.go2rust.toml" | cut -d'"' -f2)
+    fi
+    
+    # Build transpile command with appropriate flags
+    local transpile_cmd="./go2rust"
+    if [ -n "$external_mode" ]; then
+        transpile_cmd="$transpile_cmd --external-packages=$external_mode"
+    fi
+    transpile_cmd="$transpile_cmd \"$test_dir\""
+    
     # Transpile to Rust
-    transpile_output=$(./go2rust "$test_dir" 2>&1)
+    transpile_output=$(eval $transpile_cmd 2>&1)
     if [ $? -ne 0 ]; then
         echo "Transpilation failed:"
         echo "$transpile_output" | sed "s/^/  /"
@@ -307,6 +321,10 @@ run_xfail_test() {
     run_test "tests/error_simple"
 }
 
+@test "external_simple" {
+    run_test "tests/external_simple"
+}
+
 @test "fmt_println" {
     run_test "tests/fmt_println"
 }
@@ -567,10 +585,6 @@ run_xfail_test() {
     run_xfail_test "tests/XFAIL/external_packages"
 }
 
-@test "XFAIL: external_simple" {
-    run_xfail_test "tests/XFAIL/external_simple"
-}
-
 @test "XFAIL: fallthrough_switch" {
     run_xfail_test "tests/XFAIL/fallthrough_switch"
 }