Add python support to maven plugin (#857)

plugin-maven/CHANGES.md

@@ -3,6 +3,8 @@
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `1.27.0`).
 
 ## [Unreleased]
+### Added
+* Added support for [python](README.md#python), specifically [black](README.md#black).
 ### Changed
 * Update ktfmt from 0.21 to 0.24
 ### Fixed

plugin-maven/README.md

@@ -52,6 +52,7 @@ user@machine repo % mvn spotless:check
   - [Kotlin](#kotlin) ([ktfmt](#ktfmt), [ktlint](#ktlint), [diktat](#diktat), [prettier](#prettier))
   - [Scala](#scala) ([scalafmt](#scalafmt))
   - [C/C++](#cc) ([eclipse cdt](#eclipse-cdt))
+  - [Python](#python) ([black](#black))
   - [Antlr4](#antlr4) ([antlr4formatter](#antlr4formatter))
   - [Sql](#sql) ([dbeaver](#dbeaver))
   - [Typescript](#typescript) ([tsfmt](#tsfmt), [prettier](#prettier))
@@ -397,6 +398,42 @@ Groovy-Eclipse formatting errors/warnings lead per default to a build failure. T
 </eclipseCdt>
 ```
 
+## Python
+
+[code](https://github.com/diffplug/spotless/blob/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/python/Python.java). [available steps](https://github.com/diffplug/spotless/tree/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/python/Black.java).
+
+```xml
+<configuration>
+  <python>
+    <!-- You have to set the target manually -->
+    <includes>
+      <include>src/main/**/*.py</include>
+    </includes>
+
+    <black />  <!-- has its own section below -->
+  </python>
+</configuration>
+```
+
+### black
+
+[homepage](https://github.com/psf/black). [changelog](https://github.com/psf/black/blob/master/CHANGES.md).
+
+```xml
+<black>
+  <version>19.10b0</version> <!-- optional -->
+  <!-- if black is not on your path, you must specify its location manually -->
+  <pathToExe>C:/myuser/.pyenv/versions/3.8.0/scripts/black.exe</pathToExe>
+  <!--
+    Spotless always checks the version of the black it is using
+    and will fail with an error if it does not match the expected version
+    (whether manually specified or default). If there is a problem, Spotless
+    will suggest commands to help install the correct version.
+    TODO: handle installation & packaging automatically - https://github.com/diffplug/spotless/issues/674
+  -->
+</black>
+```
+
 ## Antlr4
 
 [code](https://github.com/diffplug/spotless/blob/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/antlr4/Antlr4.java). [available steps](https://github.com/diffplug/spotless/tree/main/plugin-maven/src/main/java/com/diffplug/spotless/maven/antlr4).

plugin-maven/src/main/java/com/diffplug/spotless/maven/AbstractSpotlessMojo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2020 DiffPlug
+ * Copyright 2016-2021 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -56,6 +56,7 @@
 import com.diffplug.spotless.maven.groovy.Groovy;
 import com.diffplug.spotless.maven.java.Java;
 import com.diffplug.spotless.maven.kotlin.Kotlin;
+import com.diffplug.spotless.maven.python.Python;
 import com.diffplug.spotless.maven.scala.Scala;
 import com.diffplug.spotless.maven.sql.Sql;
 import com.diffplug.spotless.maven.typescript.Typescript;
@@ -122,6 +123,9 @@ public abstract class AbstractSpotlessMojo extends AbstractMojo {
 	@Parameter
 	private Sql sql;
 
+	@Parameter
+	private Python python;
+
 	@Parameter(property = "spotlessFiles")
 	private String filePatterns;
 
@@ -254,7 +258,7 @@ private FileLocator getFileLocator() {
 	}
 
 	private List<FormatterFactory> getFormatterFactories() {
-		return Stream.concat(formats.stream(), Stream.of(groovy, java, scala, kotlin, cpp, typescript, antlr4, sql))
+		return Stream.concat(formats.stream(), Stream.of(groovy, java, scala, kotlin, cpp, typescript, antlr4, sql, python))
 				.filter(Objects::nonNull)
 				.collect(toList());
 	}

plugin-maven/src/main/java/com/diffplug/spotless/maven/python/Black.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2021 DiffPlug
+ *
+ * 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.
+ */
+package com.diffplug.spotless.maven.python;
+
+import org.apache.maven.plugins.annotations.Parameter;
+
+import com.diffplug.spotless.FormatterStep;
+import com.diffplug.spotless.maven.FormatterStepConfig;
+import com.diffplug.spotless.maven.FormatterStepFactory;
+import com.diffplug.spotless.python.BlackStep;
+
+public class Black implements FormatterStepFactory {
+
+	@Parameter
+	private String version;
+
+	@Parameter
+	private String pathToExe;
+
+	@Override
+	public FormatterStep newFormatterStep(FormatterStepConfig stepConfig) {
+		BlackStep black = BlackStep.withVersion(version == null ? BlackStep.defaultVersion() : version);
+		if (pathToExe != null) {
+			black = black.withPathToExe(pathToExe);
+		}
+		return black.create();
+	}
+}

plugin-maven/src/main/java/com/diffplug/spotless/maven/python/Python.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2021 DiffPlug
+ *
+ * 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.
+ */
+package com.diffplug.spotless.maven.python;
+
+import java.util.Collections;
+import java.util.Set;
+
+import com.diffplug.spotless.maven.FormatterFactory;
+import com.diffplug.spotless.maven.generic.LicenseHeader;
+
+/**
+ * A {@link FormatterFactory} implementation that corresponds to {@code <python>...</python>} configuration element.
+ * <p>
+ * It defines a formatter for python source files that can execute both language agnostic (e.g. {@link LicenseHeader})
+ * and python-specific (e.g. {@link Black}) steps.
+ */
+public class Python extends FormatterFactory {
+
+	@Override
+	public Set<String> defaultIncludes() {
+		return Collections.emptySet();
+	}
+
+	@Override
+	public String licenseHeaderDelimiter() {
+		return null;
+	}
+
+	public void addBlack(Black black) {
+		addStepFactory(black);
+	}
+
+}