Allow configuration of P2 mirror for spotless (#64)

This fixes #58

README.md

@@ -104,6 +104,8 @@ By default uses [this configuration](./src/main/resources/config/spotless/eclips
 * `dk.mada.style.formatter.eclipse-config-path = null`  
  Optional path to an alternative eclipse formatter configuration file
  This can be a URL; the content will be downloaded and cached (so if you want to update the content, you must change the URL)
+* `dk.mada.style.formatter.eclipse-429-p2-url = null`
+ Optional URL to a P2 update repository containing Eclipse 4.29 (aka 2023.09) plugins.
 
 **Null-checker**
 

src/main/java/dk/mada/style/config/PluginConfiguration.java

@@ -64,12 +64,14 @@ public record ErrorProneConfiguration(boolean enabled, boolean ignoreTestSource,
     /**
      * Formatter configuration.
      *
-     * @param enabled           flag to activate formatter
-     * @param include           Ant-style pattern for sources to format
-     * @param exclude           Ant-style pattern for sources to ignore
-     * @param eclipseConfigPath an optional path to an eclipse configuration file
+     * @param enabled            flag to activate formatter
+     * @param include            Ant-style pattern for sources to format
+     * @param exclude            Ant-style pattern for sources to ignore
+     * @param eclipseConfigPath  an optional path to an eclipse configuration file
+     * @param eclipse429P2mirror an optional URL to a eclipse update P2 repository
      */
-    public record FormatterConfiguration(boolean enabled, String include, String exclude, @Nullable String eclipseConfigPath) {
+    public record FormatterConfiguration(boolean enabled, String include, String exclude, @Nullable String eclipseConfigPath,
+            @Nullable String eclipse429P2mirror) {
     }
 
     /**
@@ -124,7 +126,8 @@ public PluginConfiguration(Project project) {
                 getBoolProperty("formatter.enabled", true),
                 getProperty("formatter.include", "src/main/java/**/*.java"),
                 getProperty("formatter.exclude", ""),
-                getNullableProperty("formatter.eclipse-config-path", null));
+                getNullableProperty("formatter.eclipse-config-path", null),
+                getNullableProperty("formatter.eclipse-429-p2-url", null));
 
         nullcheckerConf = new NullcheckerConfiguration(
                 getBoolProperty("null-checker.enabled", true),

src/main/java/dk/mada/style/configurators/SpotlessConfigurator.java

@@ -1,10 +1,12 @@
 package dk.mada.style.configurators;
 
 import java.nio.file.Path;
+import java.util.Map;
 
 import org.gradle.api.logging.Logger;
 
 import com.diffplug.gradle.spotless.JavaExtension;
+import com.diffplug.gradle.spotless.JavaExtension.EclipseConfig;
 import com.diffplug.gradle.spotless.SpotlessExtension;
 
 import dk.mada.style.config.ConfigFileExtractor;
@@ -61,7 +63,14 @@ private void configureJava(JavaExtension je) {
         je.target(include);
         je.targetExclude(exclude);
 
-        je.eclipse().configFile(configFile);
+        EclipseConfig eclipseConfig = je.eclipse();
+        eclipseConfig.configFile(configFile);
+
+        String p2Mirror = formatterConfig.eclipse429P2mirror();
+        if (p2Mirror != null) {
+            eclipseConfig.withP2Mirrors(Map.of("https://download.eclipse.org/eclipse/updates/4.29/", p2Mirror));
+        }
+
         je.formatAnnotations(); // Note that this *must* come after the java formatter configuration
     }