introduce ExternalCompiler.isCompilableFile() method

java/compiler/impl/src/com/intellij/compiler/impl/javaCompiler/ExternalCompiler.java

@@ -19,6 +19,7 @@ import com.intellij.openapi.compiler.CompileContext;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.fileTypes.FileType;
 import com.intellij.openapi.fileTypes.StdFileTypes;
+import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.util.EnvironmentUtil;
 import com.intellij.util.StringBuilderSpinAllocator;
 import org.jetbrains.annotations.NonNls;
@@ -41,6 +42,18 @@ public abstract class ExternalCompiler implements BackendCompiler {
     return COMPILABLE_TYPES;
   }
 
+  /**
+   * Checks if the compiler can compile the specified file.
+   *
+   * @param file    the file to check.
+   * @param context the context for the current compile operation.
+   * @return true if can compile the file, false otherwise. If the method returns false, <code>file</code>
+   *         will not be included in the list of files passed to {@link #compile(CompileContext, com.intellij.util.Chunk < com.intellij.openapi.module.Module >,com.intellij.openapi.vfs.VirtualFile[], com.intellij.openapi.compiler.TranslatingCompiler.OutputSink)}.
+   */
+  public boolean isCompilableFile(VirtualFile file, CompileContext context) {
+    return getCompilableFileTypes().contains(file.getFileType());
+  }
+
   @NotNull
   public Process launchProcess(@NotNull final ModuleChunk chunk, @NotNull final String outputDir, @NotNull final CompileContext compileContext) throws IOException {
     final String[] commands = createStartupCommand(chunk, compileContext, outputDir);

java/compiler/impl/src/com/intellij/compiler/impl/javaCompiler/JavaCompiler.java

@@ -50,7 +50,11 @@ public class JavaCompiler implements TranslatingCompiler {
   }
 
   public boolean isCompilableFile(VirtualFile file, CompileContext context) {
-    return getBackEndCompiler().getCompilableFileTypes().contains(file.getFileType());
+    final BackendCompiler backEndCompiler = getBackEndCompiler();
+    if (backEndCompiler instanceof ExternalCompiler) {
+      return ((ExternalCompiler)backEndCompiler).isCompilableFile(file, context);
+    }
+    return backEndCompiler.getCompilableFileTypes().contains(file.getFileType());
   }
 
   public void compile(CompileContext context, Chunk<Module> moduleChunk, VirtualFile[] files, OutputSink sink) {