[java] IDEA-355048 Support binary files (.class) in split mode.

- support kotlin compiled classes

GitOrigin-RevId: 8a1ec87426603d017068bb2f311edb105fa5e977

java/java-frontback-psi-api/src/com/intellij/psi/compiled/ClassFileDecompilers.java

@@ -0,0 +1,89 @@
+// Copyright 2000-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.psi.compiled;
+
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.components.Service;
+import com.intellij.openapi.extensions.ExtensionPointName;
+import com.intellij.openapi.fileTypes.BinaryFileTypeDecompilers;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.psi.FileViewProvider;
+import com.intellij.psi.PsiManager;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * An API to extend default IDEA .class file decompiler and handle files compiled from sources other than Java.
+ */
+@Service
+public final class ClassFileDecompilers {
+  /**
+   * Actual implementations should extend either {@link Light} or {@link Full} classes -
+   * those that don't are silently ignored.
+   */
+  public interface Decompiler {
+    boolean accepts(@NotNull VirtualFile file);
+  }
+
+  /**
+   * <p>"Light" decompilers are intended for augmenting file text constructed by standard IDEA decompiler
+   * without changing it's structure - i.e. providing additional information in comments,
+   * or replacing standard "compiled code" method body comment with something more meaningful.</p>
+   *
+   * <p>If a plugin by somewhat reason cannot decompile a file it can throw {@link Light.CannotDecompileException}
+   * and thus make IDEA to fall back to a built-in decompiler implementation.</p>
+   *
+   * <p>Plugins registering extension of this type normally should accept all files and use {@code order="last"}
+   * attribute to avoid interfering with other decompilers.</p>
+   */
+  public abstract static class Light implements Decompiler {
+    public static class CannotDecompileException extends RuntimeException {
+      public CannotDecompileException(String message, Throwable cause) {
+        super(message, cause);
+      }
+    }
+
+    @NotNull
+    public abstract CharSequence getText(@NotNull VirtualFile file) throws CannotDecompileException;
+  }
+
+  /**
+   * <p>"Full" decompilers are designed to provide extended support for languages significantly different from Java.
+   * Extensions of this type should take care of building file stubs and properly indexing them -
+   * in return they have an ability to represent decompiled file in a way natural for original language.</p>
+   */
+  public abstract static class Full implements Decompiler {
+    @NotNull
+    public abstract ClsStubBuilder getStubBuilder();
+
+    /**
+     * <h5>Notes for implementers</h5>
+     *
+     * <p>1. Return a correct language from {@link FileViewProvider#getBaseLanguage()}.</p>
+     *
+     * <p>2. This method is called for both PSI file construction and obtaining document text.
+     * In the latter case the PsiManager is based on default project, and the only method called
+     * on a resulting view provider is {@link FileViewProvider#getContents()}.</p>
+     *
+     * <p>3. A language compiler may produce auxiliary .class files which should be handled as part of their parent classes.
+     * A standard practice is to hide such files by returning {@code null} from
+     * {@link FileViewProvider#getPsi(com.intellij.lang.Language)}.</p>
+     */
+    @NotNull
+    public abstract FileViewProvider createFileViewProvider(@NotNull VirtualFile file, @NotNull PsiManager manager, boolean physical);
+  }
+
+  public static ClassFileDecompilers getInstance() {
+    return ApplicationManager.getApplication().getService(ClassFileDecompilers.class);
+  }
+
+  public final ExtensionPointName<Decompiler> EP_NAME = new ExtensionPointName<>("com.intellij.psi.classFileDecompiler");
+
+  private ClassFileDecompilers() {
+    Runnable runnable = () -> BinaryFileTypeDecompilers.getInstance().notifyDecompilerSetChange();
+    EP_NAME.addChangeListener(runnable, null);
+  }
+
+  @SuppressWarnings("unchecked")
+  public <D extends Decompiler> D find(@NotNull VirtualFile file, @NotNull Class<D> decompilerClass) {
+    return (D)EP_NAME.findFirstSafe(d -> decompilerClass.isInstance(d) && d.accepts(file));
+  }
+}

java/java-frontback-psi-api/src/com/intellij/psi/compiled/ClsStubBuilder.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2000-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.psi.compiled;
+
+import com.intellij.psi.stubs.PsiFileStub;
+import com.intellij.util.cls.ClsFormatException;
+import com.intellij.util.indexing.FileContent;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public abstract class ClsStubBuilder {
+  /**
+   * Non-zero positive number expected.
+   */
+  public abstract int getStubVersion();
+
+  /**
+   * May return {@code null} for inner or synthetic classes - i.e. those indexed as a part of their parent .class file.
+   */
+  @Nullable
+  public abstract PsiFileStub<?> buildFileStub(@NotNull FileContent fileContent) throws ClsFormatException;
+}