fix: use language substitor

src/main/java/com/redhat/devtools/lsp4ij/LSPIJUtils.java

@@ -448,6 +448,16 @@ private static boolean doOpenInEditor(@NotNull VirtualFile file,
         }
     }
 
+    @NotNull
+    public static Language getFileLanguage(@NotNull PsiFile file) {
+        // file.getLanguage() returns the initial file language
+        // but doesn't take care of the LanguageSubstitutor
+        // In IJ Quarkus, HTML file language becomes Qute file language by using the QuteLanguageSubstitutor
+        // - file.getLanguage() -> HTML language
+        // - file.getViewProvider().getBaseLanguage() -> Qute language
+        return file.getViewProvider().getBaseLanguage();
+    }
+
     /**
      * Returns the file language of the given file and null otherwise.
      *
@@ -1423,4 +1433,5 @@ public static String getProjectUri(Project project) {
                 .map(l -> new LocationData(new Location(l.getTargetUri(), l.getTargetSelectionRange() != null ? l.getTargetSelectionRange() : l.getTargetRange()), languageServer))
                 .toList();
     }
+
 }

src/main/java/com/redhat/devtools/lsp4ij/LanguageServersRegistry.java

@@ -512,7 +512,7 @@ public boolean isFileSupported(@Nullable PsiFile file) {
         if (file == null) {
             return false;
         }
-        Language language = file.getLanguage();
+        Language language = LSPIJUtils.getFileLanguage(file);
         FileType fileType = file.getFileType();
         return isFileSupported(language, fileType, file.getName(), null, file, file.getProject());
     }

src/main/java/com/redhat/devtools/lsp4ij/LanguageServiceAccessor.java

@@ -484,7 +484,7 @@ private MatchedLanguageServerDefinitions getMatchedLanguageServerDefinitions(@No
         // look for running language servers via content-type
         Queue<Object> languages = new LinkedList<>();
         Set<Object> processedContentTypes = new HashSet<>();
-        Language language = psiFile.getLanguage();
+        Language language = LSPIJUtils.getFileLanguage(psiFile);
         if (language != null) {
             languages.add(language);
         }

src/main/java/com/redhat/devtools/lsp4ij/client/indexing/ProjectIndexingManager.java

@@ -118,10 +118,11 @@ private synchronized static CompletableFuture<Void> initialize() {
      * @return the execute LSP feature status for the given Psi file.
      */
     public static ExecuteLSPFeatureStatus canExecuteLSPFeature(@Nullable PsiFile file) {
-        if (file == null) {
+        if (file == null || !LanguageServersRegistry.getInstance().isFileSupported(file)) {
+            // The file is not associated to a language server, don't execute the LSP feature.
             return ExecuteLSPFeatureStatus.NOT;
         }
-        return canExecuteLSPFeature(file.getVirtualFile(), file.getProject());
+        return doCanExecuteLSPFeature(file.getVirtualFile(), file.getProject());
     }
 
     /**
@@ -137,6 +138,11 @@ public static ExecuteLSPFeatureStatus canExecuteLSPFeature(@Nullable VirtualFile
             // The file is not associated to a language server, don't execute the LSP feature.
             return ExecuteLSPFeatureStatus.NOT;
         }
+        return doCanExecuteLSPFeature(file, project);
+    }
+
+    private static @NotNull ExecuteLSPFeatureStatus doCanExecuteLSPFeature(@Nullable VirtualFile file,
+                                                                           @NotNull Project project) {
         ProjectIndexingManager manager = getInstance(project);
         if (manager.isIndexingAll()) {
             // The file is associated to a language server, but the project is indexing