Added partial Groovy language support (#833)

docs/01-about/020_programming-languages.md

@@ -31,6 +31,8 @@ With Serena, we provide direct, out-of-the-box support for:
   (requires installation of fortls: `pip install fortls`)
 * **Go**  
   (requires installation of `gopls`)
+* **Groovy**  
+  (requires local groovy-language-server.jar setup via GROOVY_LS_JAR_PATH or configuration)
 * **Haskell**  
   (automatically locates HLS via ghcup, stack, or system PATH; supports Stack and Cabal projects)
 * **Java**  

docs/03-special-guides/groovy_setup_guide_for_serena.md

@@ -0,0 +1,88 @@
+# Groovy Setup Guide for Serena
+
+The Groovy support in Serena is incomplete and requires the user to provide a functioning,
+JVM-based Groovy language server as a jar. This intermediate state allows the contributors
+of Groovy support to use Serena internally and hopefully to accelerate their open-source
+release of a Groovy language server in the future.
+
+If you happen to have a Groovy language server JAR file, you can configure Serena to use it
+by following the instructions below.
+
+---
+## Prerequisites
+
+- Groovy Language Server JAR file
+    - Can be any open-source Groovy language server or your custom implementation
+    - The JAR must be compatible with standard LSP protocol
+
+---
+## Configuration
+
+Configure Groovy Language Server by adding settings to your `~/.serena/serena_config.yml`:
+
+### Basic Configuration
+
+```yaml
+ls_specific_settings:
+  groovy:
+    ls_jar_path: '/path/to/groovy-language-server.jar'
+    ls_jar_options: '-Xmx2G -Xms512m'
+```
+
+### Custom Java Paths
+
+If you have specific Java installations:
+
+```yaml
+ls_specific_settings:
+  groovy:
+    ls_jar_path: '/path/to/groovy-language-server.jar'
+    ls_java_home_path: '/usr/lib/jvm/java-21-openjdk'  # Custom JAVA_HOME directory
+    ls_jar_options: '-Xmx2G -Xms512m'                  # Optional JVM options
+```
+
+### Configuration Options
+
+- `ls_jar_path`: Absolute path to your Groovy Language Server JAR file (required)
+- `ls_java_home_path`: Custom JAVA_HOME directory for Java installation (optional)
+    - When specified, Serena will use this Java installation instead of downloading bundled Java
+    - Java executable path is automatically determined based on platform:
+        - Windows: `{ls_java_home_path}/bin/java.exe`
+        - Linux/macOS: `{ls_java_home_path}/bin/java`
+    - Validates that Java executable exists at the expected location
+- `ls_jar_options`: JVM options for language server (optional)
+    - Common options:
+        - `-Xmx<size>`: Maximum heap size (e.g., `-Xmx2G` for 2GB)
+        - `-Xms<size>`: Initial heap size (e.g., `-Xms512m` for 512MB)
+
+---
+## Project Structure Requirements
+
+For optimal Groovy Language Server performance, ensure your project follows standard Groovy/Gradle structure:
+
+```
+project-root/
+├── src/
+│   ├── main/
+│   │   ├── groovy/
+│   │   └── resources/
+│   └── test/
+│       ├── groovy/
+│       └── resources/
+├── build.gradle or build.gradle.kts
+├── settings.gradle or settings.gradle.kts
+└── gradle/
+    └── wrapper/
+```
+
+---
+## Using Serena with Groovy
+
+- Serena automatically detects Groovy files (`*.groovy`, `*.gvy`) and will start a Groovy Language Server JAR process per project when needed.
+- Optimal results require that your project compiles successfully via Gradle or Maven. If compilation fails, fix build errors in your build tool first.
+
+## Reference
+
+- **Groovy Documentation**: [https://groovy-lang.org/documentation.html](https://groovy-lang.org/documentation.html)
+- **Gradle Documentation**: [https://docs.gradle.org](https://docs.gradle.org)
+- **Serena Configuration**: [../02-usage/050_configuration.md](../02-usage/050_configuration.md)