[CompilerPlugin] remove _resolveMacro

That was only just a thunk for testing. Use @_spi(Testing) instead.

Author: rintaro

Sources/SwiftCompilerPlugin/CompilerPlugin.swift

@@ -63,7 +63,8 @@ public protocol CompilerPlugin {
 }
 
 extension CompilerPlugin {
-  func resolveMacro(moduleName: String, typeName: String) throws -> Macro.Type {
+  @_spi(Testing)
+  public func resolveMacro(moduleName: String, typeName: String) throws -> Macro.Type {
     let qualifedName = "\(moduleName).\(typeName)"
 
     for type in providingMacros {
@@ -78,11 +79,6 @@ extension CompilerPlugin {
     let pluginPath = CommandLine.arguments.first ?? Bundle.main.executablePath ?? ProcessInfo.processInfo.processName
     throw CompilerPluginError(message: "macro implementation type '\(moduleName).\(typeName)' could not be found in executable plugin '\(pluginPath)'")
   }
-
-  // @testable
-  public func _resolveMacro(moduleName: String, typeName: String) -> Macro.Type? {
-    try? resolveMacro(moduleName: moduleName, typeName: typeName)
-  }
 }
 
 struct MacroProviderAdapter<Plugin: CompilerPlugin>: PluginProvider {

Tests/SwiftCompilerPluginTest/CompilerPluginTests.swift

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-import SwiftCompilerPlugin
+@_spi(Testing) import SwiftCompilerPlugin
 import SwiftSyntax
 import SwiftSyntaxMacros
 import XCTest
@@ -51,20 +51,18 @@ public class CompilerPluginTests: XCTestCase {
   func testResolveMacro() {
     let plugin = MyPlugin()
 
-    let registeredMacro = plugin._resolveMacro(
+    let registeredMacro = try? plugin.resolveMacro(
       moduleName: "SwiftCompilerPluginTest",
       typeName: "RegisteredMacro"
     )
     XCTAssertNotNil(registeredMacro)
     XCTAssertTrue(registeredMacro == RegisteredMacro.self)
 
     /// Test the plugin doesn't provide unregistered macros.
-    let dummyMacro = plugin._resolveMacro(
+    XCTAssertThrowsError(try plugin.resolveMacro(
       moduleName: "SwiftCompilerPluginTest",
       typeName: "DummyMacro"
-    )
-    XCTAssertNil(dummyMacro)
-    XCTAssertFalse(dummyMacro == DummyMacro.self)
+    ))
 
   }
 }