[maven] Introduce addTestCompileSourceRoot (#6120)

modules/openapi-generator-maven-plugin/README.md

@@ -96,7 +96,8 @@ mvn clean compile
 | `withXml` |  `openapi.generator.maven.plugin.withXml` | enable XML annotations inside the generated models and API (only works with Java `language` and libraries that provide support for JSON and XML)
 | `skip` |  `codegen.skip` | skip code generation (`false` by default. Can also be set globally through the `codegen.skip` property)
 | `skipIfSpecIsUnchanged` |  `codegen.skipIfSpecIsUnchanged` | Skip the execution if the source file is older than the output folder (`false` by default. Can also be set globally through the `codegen.skipIfSpecIsUnchanged` property)
-| `addCompileSourceRoot` |  `openapi.generator.maven.plugin.addCompileSourceRoot` | add the output directory to the project as a source root (`true` by default)
+| `addCompileSourceRoot` |  `openapi.generator.maven.plugin.addCompileSourceRoot` | Add the output directory to the project as a source root, so that the generated java types are compiled and included in the project artifact (`true` by default). Mutually exclusive with `addTestCompileSourceRoot`.
+| `addTestCompileSourceRoot` |  `openapi.generator.maven.plugin.addTestCompileSourceRoot` | Add the output directory to the project as a test source root, so that the generated java types are compiled only for the test classpath of the project (`false` by default). Mutually exclusive with `addCompileSourceRoot`.
 | `environmentVariables` | N/A | A **map** of items conceptually similar to "environment variables" or "system properties". These are merged into a map of global settings available to all aspects of the generation flow. Use this map for any options documented elsewhere as `systemProperties`.
 | `configHelp` |  `codegen.configHelp` | dumps the configuration help for the specified library (generates no sources)
 

modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java

@@ -403,11 +403,18 @@ public class CodeGenMojo extends AbstractMojo {
 
     /**
      * Add the output directory to the project as a source root, so that the generated java types
-     * are compiled and included in the project artifact.
+     * are compiled and included in the project artifact. Mutually exclusive with {@link #addTestCompileSourceRoot}.
      */
     @Parameter(defaultValue = "true", property = "openapi.generator.maven.plugin.addCompileSourceRoot")
     private boolean addCompileSourceRoot = true;
 
+    /**
+     * Add the output directory to the project as a test source root, so that the generated java types
+     * are compiled only for the test classpath of the project. Mutually exclusive with {@link #addCompileSourceRoot}.
+     */
+    @Parameter(defaultValue = "false", property = "openapi.generator.maven.plugin.addTestCompileSourceRoot")
+    private boolean addTestCompileSourceRoot = false;
+
     // TODO: Rename to global properties in version 5.0
     @Parameter
     protected Map<String, String> environmentVariables = new HashMap<>();
@@ -431,6 +438,7 @@ public class CodeGenMojo extends AbstractMojo {
     @Override
     public void execute() throws MojoExecutionException {
         File inputSpecFile = new File(inputSpec);
+        resetEnvironmentVariables();
         addCompileSourceRootIfConfigured();
 
         try {
@@ -848,17 +856,28 @@ public class CodeGenMojo extends AbstractMojo {
         final Object sourceFolderObject =
                 configOptions == null ? null : configOptions
                         .get(CodegenConstants.SOURCE_FOLDER);
-        final String sourceFolder =
-                sourceFolderObject == null ? "src/main/java" : sourceFolderObject.toString();
+        final String sourceFolder;
+        if (sourceFolderObject != null) {
+            sourceFolder = sourceFolderObject.toString();
+        } else {
+            sourceFolder = addTestCompileSourceRoot ? "src/test/java" : "src/main/java";
+        }
 
         return output.toString() + "/" + sourceFolder;
     }
 
-    private void addCompileSourceRootIfConfigured() {
+    private void addCompileSourceRootIfConfigured() throws MojoExecutionException {
         if (addCompileSourceRoot) {
+            if (addTestCompileSourceRoot) {
+                throw new MojoExecutionException("Either 'addCompileSourceRoot' or 'addTestCompileSourceRoot' may be active, not both.");
+            }
             project.addCompileSourceRoot(getCompileSourceRoot());
+        } else if (addTestCompileSourceRoot) {
+            project.addTestCompileSourceRoot(getCompileSourceRoot());
         }
+    }
 
+    private void resetEnvironmentVariables() {
         // Reset all environment variables to their original value. This prevents unexpected
         // behaviour
         // when running the plugin multiple consecutive times with different configurations.