Fix command plugin when run on targets with dependencies (#801)

### Motivation

The command plugin is used for ahead-of-time (AOT) code generation. It
can be run with `--target`, or without, in which case it considers all
targets based on the presence of the requisite OpenAPI document and
config file.

If a target is detected that doesn't have either of these files, it
should be considered an error if that target was explicitly asked for
using `--target`. If it wasn't—either because we're looking at all
targets, or because it is a dependency—it should be skipped.

### Modifications

- Extend integration test to repro issue for AOT targets with
dependencies
- Skip targets that have no requisite files for generation unless they
were asked for

### Result

Fixes command plugin when used for AOT generation with targets with
target dependencies.

### Test Plan

This PR starts out with a commit that updated the integration test to
repro the issue, which we should see fail in CI. Only then was a commit
added to address the issue, restoring the CI to green.

Author: simonjbeaumont

.licenseignore

@@ -43,3 +43,4 @@ Examples/streaming-chatgpt-proxy/players.txt
 **/Makefile
 **/*.html
 .editorconfig
+IntegrationTest/**/Empty.swift

IntegrationTest/Package.swift

@@ -51,5 +51,12 @@ let package = Package(
             name: "MockTransportServer",
             dependencies: ["Server", .product(name: "OpenAPIRuntime", package: "swift-openapi-runtime")]
         ),
+        // Targets to integration test the command plugin
+        .target(name: "Empty"),
+        .target(name: "TypesAOT", dependencies: [.product(name: "OpenAPIRuntime", package: "swift-openapi-runtime")]),
+        .target(
+            name: "TypesAOTWithDependency",
+            dependencies: ["Empty", .product(name: "OpenAPIRuntime", package: "swift-openapi-runtime")]
+        ),
     ]
 )

IntegrationTest/Sources/Empty/Empty.swift

@@ -0,0 +1,4 @@
+generate:
+  - types
+accessModifier: package
+namingStrategy: idiomatic

IntegrationTest/Sources/TypesAOT/Empty.swift

@@ -0,0 +1 @@
+../openapi.yaml

IntegrationTest/Sources/TypesAOT/openapi-generator-config.yaml

@@ -0,0 +1,4 @@
+generate:
+  - types
+accessModifier: package
+namingStrategy: idiomatic

IntegrationTest/Sources/TypesAOT/openapi.yaml

@@ -0,0 +1 @@
+../openapi.yaml

IntegrationTest/Sources/TypesAOTWithDependency/Empty.swift

@@ -81,16 +81,23 @@ extension SwiftOpenAPIGeneratorPlugin: CommandPlugin {
                 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),
+                if 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
+                    // The error is that neither of the required files are present for code generation for this target.
+                    // This should only be considered an error if this target was explicitly provided as a target for
+                    // code generation with --target.
+                    // We may get this error for other targets if:
+                    //
+                    // 1. The command plugin was run with no --target arguments, in which case the plugin loops over
+                    //    all targets; or
+                    // 2. This target is a dependency of a target that was requested using --target.
+                    //
+                    // In either of these cases, we should not consider this an error and skip the target.
+                    if !targetNameArguments.contains(target.name) {
+                        log("- Skipping because target isn't configured for OpenAPI code generation.")
+                        continue
+                    }
                 }
 
                 if error.isMisconfigurationError {