IDEA-281375 Don't run formatter on save on syntactically invalid file

GitOrigin-RevId: 2e610c2bebbe72325b51c8e95e9006c8e0a03c8d

platform/code-style-api/src/com/intellij/lang/LanguageFormatting.java

@@ -7,6 +7,7 @@ import com.intellij.formatting.FormattingModelBuilder;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.codeStyle.ExternalFormatProcessor;
+import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -55,4 +56,15 @@ public final class LanguageFormatting extends LanguageExtension<FormattingModelB
     }
     return null;
   }
+
+  /**
+   * Checks if automatic reformat is allowed for the given context element using {@link LanguageFormattingRestriction} extensions.
+   *
+   * @param context The element to check.
+   *
+   * @return True if formatting is allowed, false otherwise.
+   */
+  public boolean isAutoFormatAllowed(@NotNull PsiElement context) {
+    return ContainerUtil.and(LanguageFormattingRestriction.EP_NAME.getExtensionList(), each -> each.isAutoFormatAllowed(context));
+  }
 }

platform/code-style-api/src/com/intellij/lang/LanguageFormattingRestriction.java

@@ -24,4 +24,19 @@ public interface LanguageFormattingRestriction {
     "com.intellij.lang.formatter.restriction");
 
   boolean isFormatterAllowed(@NotNull PsiElement context);
+
+  /**
+   * Checks if automatic code reformat is allowed, for example, on save. By default, the method returns the same value as
+   * {@link #isFormatterAllowed(PsiElement)} used for explicit reformat.
+   *
+   * @param context A context element.
+   *
+   * @return True if automatic reformat is allowed, false to block it. For automatic formatting to work, this method and
+   * {@link #isFormatterAllowed(PsiElement)} must <i>both</i> return {@code true}.
+   *
+   * @see LanguageFormatting#isAutoFormatAllowed(PsiElement)
+   */
+  default boolean isAutoFormatAllowed(@NotNull PsiElement context) {
+    return isFormatterAllowed(context);
+  }
 }

platform/code-style-impl/src/com/intellij/lang/InvalidPsiAutoFormatRestriction.java

@@ -0,0 +1,24 @@
+// Copyright 2000-2021 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.lang;
+
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiErrorElement;
+import com.intellij.psi.SyntaxTraverser;
+import org.jetbrains.annotations.NotNull;
+
+public class InvalidPsiAutoFormatRestriction implements LanguageFormattingRestriction {
+  @Override
+  public boolean isFormatterAllowed(@NotNull PsiElement context) {
+    return true;
+  }
+
+  @Override
+  public boolean isAutoFormatAllowed(@NotNull PsiElement context) {
+    return context.isValid() && containsValidPsi(context);
+  }
+
+
+  private static boolean containsValidPsi(@NotNull PsiElement context) {
+    return SyntaxTraverser.psiTraverser(context).filter(PsiErrorElement.class).first() == null;
+  }
+}

platform/lang-impl/src/com/intellij/codeInsight/actions/onSave/FormatOnSaveAction.java

@@ -3,6 +3,7 @@ package com.intellij.codeInsight.actions.onSave;
 
 import com.intellij.codeInsight.actions.*;
 import com.intellij.ide.actionsOnSave.impl.ActionsOnSaveFileDocumentManagerListener;
+import com.intellij.lang.LanguageFormatting;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.project.DumbService;
 import com.intellij.openapi.project.Project;
@@ -35,7 +36,7 @@ public class FormatOnSaveAction extends ActionsOnSaveFileDocumentManagerListener
 
     for (Document document : documents) {
       PsiFile psiFile = manager.getPsiFile(document);
-      if (psiFile == null) continue;
+      if (psiFile == null || !LanguageFormatting.INSTANCE.isAutoFormatAllowed(psiFile)) continue;
 
       allFiles.add(psiFile);
 

platform/platform-resources/src/META-INF/LangExtensions.xml

@@ -1466,6 +1466,8 @@
     <lang.documentationLinkResolver implementation="com.intellij.lang.documentation.psi.PsiDocumentationLinkResolver"/>
     <projectService serviceInterface="com.intellij.lang.documentation.ide.IdeDocumentationTargetProvider"
                     serviceImplementation="com.intellij.lang.documentation.ide.impl.IdeDocumentationTargetProviderImpl"/>
+
+    <lang.formatter.restriction implementation="com.intellij.lang.InvalidPsiAutoFormatRestriction"/>
   </extensions>
   <applicationListeners>
     <listener class="com.intellij.util.indexing.FileBasedIndexPluginListener" topic="com.intellij.ide.plugins.DynamicPluginListener"/>