WIP: Generate documentation

(Manual run with `mvn exec:java@generate-bugpattern-docs -pl refaster-runner`.)

TODO: Actually hook this up in a website

error-prone-contrib/pom.xml

@@ -242,5 +242,11 @@
                 </plugin>
             </plugins>
         </pluginManagement>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
     </build>
 </project>

pom.xml

@@ -810,6 +810,11 @@
                                 <artifactId>error_prone_core</artifactId>
                                 <version>${version.error-prone}</version>
                             </path>
+                            <path>
+                                <groupId>${groupId.error-prone}</groupId>
+                                <artifactId>error_prone_docgen_processor</artifactId>
+                                <version>${version.error-prone}</version>
+                            </path>
                             <path>
                                 <groupId>com.google.auto.value</groupId>
                                 <artifactId>auto-value</artifactId>
@@ -1089,6 +1094,37 @@
                     <artifactId>build-helper-maven-plugin</artifactId>
                     <version>3.3.0</version>
                 </plugin>
+                <plugin>
+                    <groupId>org.codehaus.mojo</groupId>
+                    <artifactId>exec-maven-plugin</artifactId>
+                    <version>3.0.0</version>
+                    <configuration>
+                        <mainClass>com.google.errorprone.DocGenTool</mainClass>
+                        <arguments>
+                            <argument>-bug_patterns=${project.build.directory}/generated-sources/annotations/bugPatterns.txt</argument>
+                            <argument>-docs_repository=${project.build.directory}/generated-wiki/</argument>
+                            <argument>-explanations=${basedir}/src/main/docs/bugpattern/</argument>
+                            <argument>-target=external</argument>
+                        </arguments>
+                        <includePluginDependencies>true</includePluginDependencies>
+                    </configuration>
+                    <dependencies>
+                        <dependency>
+                            <groupId>com.google.errorprone</groupId>
+                            <artifactId>error_prone_docgen</artifactId>
+                            <version>${version.error-prone}</version>
+                        </dependency>
+                    </dependencies>
+                    <executions>
+                        <execution>
+                            <id>generate-bugpattern-docs</id>
+                            <goals>
+                                <goal>java</goal>
+                            </goals>
+                            <phase>process-classes</phase>
+                        </execution>
+                    </executions>
+                </plugin>
                 <plugin>
                     <groupId>org.codehaus.mojo</groupId>
                     <artifactId>license-maven-plugin</artifactId>

refaster-runner/src/main/docs/bugpattern/Refaster.md

@@ -0,0 +1,16 @@
+Error Prone's out-of-the-box support for the application of
+[Refaster][refaster] templates is somewhat cumbersome. Additionally, by default
+the focus of Refaster templates is on one-off code refactorings.
+
+This plugin attempts to bring Refaster templates on equal footing with other
+Error Prone plugins by locating all Refaster templates on the classpath and
+reporing any match. The suggested changes can be applied using Error Prone's
+built-in [patch][patching] functionality.
+
+XXX: Expand documentation. Mention:
+- The `refaster-resource-compiler`.
+- How checks can be restricted using the `NamePattern` flag (see the Javadoc)
+- An concrete patching example, with and without `NamePattern`.
+
+[refaster]: https://errorprone.info/docs/refaster
+[patching]: https://errorprone.info/docs/patching