fix(kotlin): compile a folder of sibling Maven projects in the Kotlin bridge (#842)

compile::plan only fell back to Gradle when the folder had no build file, so a folder of sibling Maven projects failed with "no supported build system" in the Kotlin editor compilation and Build Project. It now falls back to Maven when the model has Maven projects, after the existing Gradle fallback.

Fixes #814

Co-authored-by: ntbang0901 <[email protected]>

crates/ide-build/src/compile/mod.rs

@@ -185,8 +185,10 @@ pub fn plan(root: &Path, model: &BuildModel, kind: BuildKind, file: Option<&Path
         None => None,
     };
     let dir = module_dir.clone().unwrap_or_else(|| root.to_path_buf());
+    // A folder of sibling projects has no build file itself; its Maven projects are built one by one.
     let system = detect_dir(&dir, model, root)
         .or_else(|| if model.gradle.is_some() { Some(BuildSystem::Gradle) } else { None })
+        .or_else(|| model.maven.as_ref().filter(|m| !m.projects.is_empty()).map(|_| BuildSystem::Maven))
         .ok_or_else(|| IdeError::not_found("no supported build system (Maven, Gradle, Cargo, Go, TypeScript) found"))?;
     let module = module_dir.as_deref().filter(|d| *d != root);
     let title = match module {
@@ -814,6 +816,17 @@ mod tests {
             ("pnpm", &["run".to_owned(), "build".to_owned()][..])
         );
 
+        let siblings = tmp.path().join("siblings");
+        write(&siblings, "core/pom.xml", "<project><artifactId>core</artifactId></project>");
+        write(&siblings, "system/pom.xml", "<project><artifactId>system</artifactId></project>");
+        let model = crate::load(&siblings, &tmp.path().join("cache3"), None);
+        let p = plan(&siblings, &model, BuildKind::Build, None).unwrap();
+        assert_eq!(p.system, BuildSystem::Maven);
+        assert_eq!(
+            p.steps.iter().map(|s| s.cwd.clone()).collect::<Vec<_>>(),
+            [siblings.join("core"), siblings.join("system")]
+        );
+
         let none = tmp.path().join("none");
         std::fs::create_dir_all(&none).unwrap();
         assert!(plan(&none, &BuildModel::default(), BuildKind::Build, None).is_err());