Command plugin should skip irrelevant targets when run without --target argument (#798)

### Motivation

In #795 we adjusted the logic of the command plugin because errors were
not propagating properly. As a result, we regressed behaviour when the
command plugin was run without any `--target` argument. In this mode,
the plugin runs on all targets. When it detects a misconfigured target
it errors, as it should. However, the classification of misconfigured
target included targets that were not intended for code generation at
all, resulting in errors running the command plugin on packages with
others targets.

### Modifications

- Add command plugin generation step to integration test
- If the command plugin is running without a `--target` argument and
cannot find _any_ of the required files, skip that target.

### Result

- Manual code generation with the command plugin fixed for packages with
other targets.
- Fixes #797.

### Test Plan

This PR includes two commits. The first adds a step to the integration
test, which runs the command plugin on the integration test package.
This will fail in CI. Then the second commit will provide the fix, which
should pass in CI. The commits will then be squash merged.

Author: simonjbeaumont

Plugins/OpenAPIGeneratorCommand/plugin.swift

@@ -65,27 +65,39 @@ extension SwiftOpenAPIGeneratorPlugin: CommandPlugin {
         var hadASuccessfulRun = false
 
         for target in targets {
-            print("Considering target '\(target.name)':")
+            log("Considering target '\(target.name)':")
             guard let swiftTarget = target as? SwiftSourceModuleTarget else {
-                print("- Not a swift source module. Can't generate OpenAPI code.")
+                log("- Not a swift source module. Can't generate OpenAPI code.")
                 continue
             }
             do {
-                print("- Trying OpenAPI code generation.")
+                log("- Trying OpenAPI code generation.")
                 try runCommand(
                     targetWorkingDirectory: target.directory,
                     tool: context.tool,
                     sourceFiles: swiftTarget.sourceFiles,
                     targetName: target.name
                 )
-                print("- ✅ OpenAPI code generation for target '\(target.name)' successfully completed.")
+                log("- ✅ OpenAPI code generation for target '\(target.name)' successfully completed.")
                 hadASuccessfulRun = true
             } catch let error as PluginError {
+                if targetNameArguments.isEmpty, case .fileErrors(let errors) = error,
+                    Set(errors.map(\.fileKind)) == Set(FileError.Kind.allCases),
+                    errors.map(\.issue).allSatisfy({ $0 == FileError.Issue.noFilesFound })
+                {
+                    // The command plugin was run with no --target argument so its looping over all targets.
+                    // If a target does not have any of the required files, this should only be considered an error
+                    // if the plugin is being explicitly run on a target, either using the build plugin, or using the
+                    // command plugin with a --target argument.
+                    log("- Skipping because target isn't configured for OpenAPI code generation.")
+                    continue
+                }
+
                 if error.isMisconfigurationError {
-                    print("- Stopping because target isn't configured for OpenAPI code generation.")
+                    log("- Stopping because target is misconfigured for OpenAPI code generation.")
                     throw error
                 } else {
-                    print("- OpenAPI code generation failed with error.")
+                    log("- OpenAPI code generation failed with error.")
                     throw error
                 }
             }
@@ -94,3 +106,7 @@ extension SwiftOpenAPIGeneratorPlugin: CommandPlugin {
         guard hadASuccessfulRun else { throw PluginError.noTargetsWithExpectedFiles(targetNames: targets.map(\.name)) }
     }
 }
+
+private func log(_ message: @autoclosure () -> String) {
+    FileHandle.standardError.write(Data(message().appending("\n").utf8))
+}

Plugins/PluginsShared/PluginError.swift

@@ -14,7 +14,7 @@
 import PackagePlugin
 import Foundation
 
-enum PluginError: Swift.Error, CustomStringConvertible, LocalizedError {
+enum PluginError: Swift.Error, Equatable, CustomStringConvertible, LocalizedError {
     case incompatibleTarget(name: String)
     case generatorFailure(targetName: String)
     case noTargetsWithExpectedFiles(targetNames: [String])
@@ -55,10 +55,10 @@ enum PluginError: Swift.Error, CustomStringConvertible, LocalizedError {
     }
 }
 
-struct FileError: Swift.Error, CustomStringConvertible, LocalizedError {
+struct FileError: Swift.Error, Equatable, CustomStringConvertible, LocalizedError {
 
     /// The kind of the file.
-    enum Kind: CaseIterable {
+    enum Kind: Equatable, CaseIterable {
         /// Config file.
         case config
         /// OpenAPI document file.
@@ -73,7 +73,7 @@ struct FileError: Swift.Error, CustomStringConvertible, LocalizedError {
     }
 
     /// Encountered issue.
-    enum Issue {
+    enum Issue: Equatable {
         /// File wasn't found.
         case noFilesFound
         /// More than 1 file found.

scripts/run-integration-test.sh

@@ -45,4 +45,8 @@ swift package --package-path "${INTEGRATION_TEST_PACKAGE_PATH}" \
 log "Building integration test package: ${INTEGRATION_TEST_PACKAGE_PATH}"
 swift build --package-path "${INTEGRATION_TEST_PACKAGE_PATH}"
 
+log "Running command plugin on integration test package: ${INTEGRATION_TEST_PACKAGE_PATH}"
+swift package --package-path "${INTEGRATION_TEST_PACKAGE_PATH}" \
+ --allow-writing-to-package-directory generate-code-from-openapi
+
 log "✅ Successfully built integration test package."