[Maven] Openapi-generator-maven-plugin using configurationFile only

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

@@ -51,6 +51,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -195,6 +196,12 @@ public class CodeGenMojo extends AbstractMojo {
     @Parameter(name = "configurationFile", property = "openapi.generator.maven.plugin.configurationFile")
     private String configurationFile;
 
+    /**
+     * Skip the execution if the source file is older than the output folder.
+     */
+    @Parameter(name = "skipIfConfigurationFileMissing", property = "codegen.skipIfConfigurationFileMissing", defaultValue = "false")
+    private Boolean skipIfConfigurationFileMissing;
+
     /**
      * Specifies if the existing files should be overwritten during the generation.
      */
@@ -563,6 +570,25 @@ public class CodeGenMojo extends AbstractMojo {
 
     @Override
     public void execute() throws MojoExecutionException {
+        if (Boolean.TRUE.equals(skipIfConfigurationFileMissing) && isNotEmpty(configurationFile)) {
+            if (!new File(configurationFile).exists()) {
+                getLog().info("Code generation is skipped because configuration file [" + configurationFile + "] is missing");
+                return;
+            }
+        }
+
+        // attempt to read from config file
+        CodegenConfigurator configurator = CodegenConfigurator.fromFile(configurationFile);
+
+        // if a config file wasn't specified, or we were unable to read it
+        if (configurator == null) {
+            configurator = new CodegenConfigurator();
+        } else {
+            // retrieve mandatory fields from the configurationFile if not defined in the pom.xml
+            this.generatorName = fromConfigurator(configurator.getGeneratorName(),  generatorName);
+            this.inputSpec = fromConfigurator(configurator.getInputSpec(), inputSpec);
+        }
+
         if (StringUtils.isBlank(inputSpec) && StringUtils.isBlank(inputSpecRootDirectory)) {
             LOGGER.error("inputSpec or inputSpecRootDirectory must be specified");
             throw new MojoExecutionException("inputSpec or inputSpecRootDirectory must be specified");
@@ -638,14 +664,6 @@ public void execute() throws MojoExecutionException {
                 }
             }
 
-            // attempt to read from config file
-            CodegenConfigurator configurator = CodegenConfigurator.fromFile(configurationFile);
-
-            // if a config file wasn't specified, or we were unable to read it
-            if (configurator == null) {
-                configurator = new CodegenConfigurator();
-            }
-
             configurator.setVerbose(verbose);
 
             if (skipOverwrite != null) {
@@ -1032,6 +1050,19 @@ public void execute() throws MojoExecutionException {
         }
     }
 
+    /**
+     * Use the configurator value is not defined in the pom.xml
+     *
+     * @param defaultValue default value taking precedence
+     */
+    private <T> T fromConfigurator(T value, T defaultValue) {
+        if (defaultValue != null) {
+            // keep backward compatibilty, the value in the pom.xml has precedence over the value in the config file.
+            return defaultValue;
+        }
+        return value;
+    }
+
     /**
      * Calculate an SHA256 hash for the openapi specification.
      * If the specification is hosted on a remote resource it is downloaded first.

modules/openapi-generator-maven-plugin/src/test/java/org/openapitools/codegen/plugin/CodeGenMojoTest.java

@@ -315,6 +315,31 @@ public void test_skipIfSpecIsUnchanged_recognizesUpdatesInExternalReferencedFile
         assertTrue("Src directory should have been regenerated", Files.exists(generatedDir.resolve("src")));
     }
 
+    public void testConfigurationFile() throws Exception {
+        // GIVEN
+        CodeGenMojo mojo = loadMojo(newTempFolder(), "src/test/resources/configuration-file", null);
+
+        // WHEN
+        mojo.execute();
+
+        // THEN
+        assertEquals("spring", getVariableValueFromObject(mojo, "generatorName"));
+    }
+
+    public void testSkipConfigurationFileIfMissing() throws Exception {
+        // GIVEN
+        final Path tempDir = newTempFolder();
+        final Path generatedDir = tempDir.resolve("target/generated-sources/configuration-file-missing");
+        CodeGenMojo mojo = loadMojo(tempDir, "src/test/resources/configuration-file-missing", null);
+
+        // WHEN
+        mojo.execute();
+
+        // THEN
+        assertFalse("Src directory should not be present", Files.exists(generatedDir.resolve("src")));
+    }
+
+
     protected CodeGenMojo loadMojo(Path temporaryFolder, String projectRoot, String profile) throws Exception {
         return loadMojo(temporaryFolder, projectRoot, profile, "default");
     }

modules/openapi-generator-maven-plugin/src/test/resources/configuration-file-missing/pom.xml

@@ -0,0 +1,47 @@
+<!--
+  ~ Copyright 2020, 2021 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<project>
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>config.file.test</groupId>
+    <artifactId>not-available</artifactId>
+    <packaging>jar</packaging>
+    <version>1.0.0-SNAPSHOT</version>
+    <name>OpenAPI Generator Minimal Update Test</name>
+    <url>https://openapi-generator.tech/</url>
+    <build>
+        <finalName>No generation</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.openapitools</groupId>
+                <artifactId>openapi-generator-maven-plugin</artifactId>
+                <configuration>
+                    <configurationFile>${basedir}/config.yaml</configurationFile>
+                    <skipIfConfigurationFileMissing>true</skipIfConfigurationFileMissing>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>executionId</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>generate</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

modules/openapi-generator-maven-plugin/src/test/resources/configuration-file/config.yaml

@@ -0,0 +1,3 @@
+inputSpec: petstore-on-classpath.yaml
+generatorName: spring
+output: ./target/generated-sources/config

modules/openapi-generator-maven-plugin/src/test/resources/configuration-file/pom.xml

@@ -0,0 +1,47 @@
+<!--
+  ~ Copyright 2020, 2021 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<project>
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>config.file.test</groupId>
+    <artifactId>available</artifactId>
+    <packaging>jar</packaging>
+    <version>1.0.0-SNAPSHOT</version>
+    <name>ConfigFile</name>
+    <url>https://openapi-generator.tech/</url>
+    <build>
+        <finalName>configuration file test</finalName>
+        <plugins>
+            <plugin>
+                <groupId>org.openapitools</groupId>
+                <artifactId>openapi-generator-maven-plugin</artifactId>
+                <configuration>
+                    <configurationFile>${basedir}/config.yaml</configurationFile>
+                    <skipIfConfigurationFileMissing>true</skipIfConfigurationFileMissing>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>executionId</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>generate</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

modules/openapi-generator/src/main/java/org/openapitools/codegen/config/CodegenConfigurator.java

@@ -811,4 +811,12 @@ public ClientOptInput toClientOptInput() {
 
         return input.openAPI((OpenAPI) context.getSpecDocument());
     }
+
+    public String getGeneratorName() {
+        return generatorName;
+    }
+
+    public String getInputSpec() {
+        return inputSpec;
+    }
 }