PY-13304, PY-17979 Add option that allows to use continuation indent for arguments

python/src/com/jetbrains/python/PyBundle.properties

@@ -965,6 +965,7 @@ formatter.panel.dict.alignment.align.on.colon=Align on colon
 formatter.panel.dict.alignment.align.on.value=Align on value
 formatter.panel.dict.alignment.label=Dict alignment:
 formatter.panel.add.trailing.line.feed=Add line feed at the end of file
+formatter.panel.use.continuation.indent.for.arguments=Use continuation indent for arguments
 
 formatter.left.bracket = Left bracket
 formatter.around.eq.in.named.parameter = Around = in named parameter

python/src/com/jetbrains/python/formatter/PyBlock.java

@@ -324,7 +324,9 @@ public class PyBlock implements ASTBlock {
         childIndent = Indent.getNoneIndent();
       }
       else {
-        if (parentType == PyElementTypes.PARAMETER_LIST || argumentMayHaveSameIndentAsFollowingStatementList()) {
+        if (parentType == PyElementTypes.PARAMETER_LIST ||
+            settings.USE_CONTINUATION_INDENT_FOR_ARGUMENTS || 
+            argumentMayHaveSameIndentAsFollowingStatementList()) {
           childIndent = Indent.getContinuationIndent();
         }
         else {

python/src/com/jetbrains/python/formatter/PyCodeStylePanel.form

@@ -23,7 +23,7 @@
           </vspacer>
         </children>
       </grid>
-      <grid id="d3271" layout-manager="GridLayoutManager" row-count="2" column-count="2" same-size-horizontally="false" same-size-vertically="false" hgap="-1" vgap="-1">
+      <grid id="d3271" layout-manager="GridLayoutManager" row-count="3" column-count="2" same-size-horizontally="false" same-size-vertically="false" hgap="-1" vgap="-1">
         <margin top="10" left="10" bottom="10" right="10"/>
         <constraints>
           <grid row="0" column="0" row-span="1" col-span="1" vsize-policy="3" hsize-policy="3" anchor="0" fill="3" indent="0" use-parent-layout="false"/>
@@ -47,12 +47,20 @@
           </component>
           <component id="b4945" class="com.intellij.ui.components.JBCheckBox" binding="myAddTrailingBlankLineCheckbox" default-binding="true">
             <constraints>
-              <grid row="1" column="0" row-span="1" col-span="2" vsize-policy="0" hsize-policy="0" anchor="0" fill="0" indent="0" use-parent-layout="false"/>
+              <grid row="1" column="0" row-span="1" col-span="2" vsize-policy="0" hsize-policy="0" anchor="8" fill="0" indent="0" use-parent-layout="false"/>
             </constraints>
             <properties>
               <text resource-bundle="com/jetbrains/python/PyBundle" key="formatter.panel.add.trailing.line.feed"/>
             </properties>
           </component>
+          <component id="9e329" class="com.intellij.ui.components.JBCheckBox" binding="myUseContinuationIndentForArguments" default-binding="true">
+            <constraints>
+              <grid row="2" column="0" row-span="1" col-span="2" vsize-policy="0" hsize-policy="0" anchor="8" fill="0" indent="0" use-parent-layout="false"/>
+            </constraints>
+            <properties>
+              <text resource-bundle="com/jetbrains/python/PyBundle" key="formatter.panel.use.continuation.indent.for.arguments"/>
+            </properties>
+          </component>
         </children>
       </grid>
       <vspacer id="4e0f0">

python/src/com/jetbrains/python/formatter/PyCodeStylePanel.java

@@ -43,6 +43,7 @@ public class PyCodeStylePanel extends CodeStyleAbstractPanel {
 
   private JPanel myPanel;
   private JBCheckBox myAddTrailingBlankLineCheckbox;
+  private JBCheckBox myUseContinuationIndentForArguments;
   private ComboBox myDictAlignmentCombo;
   private JPanel myPreviewPanel;
 
@@ -71,6 +72,13 @@ public class PyCodeStylePanel extends CodeStyleAbstractPanel {
         somethingChanged();
       }
     });
+    
+    myUseContinuationIndentForArguments.addActionListener(new ActionListener() {
+      @Override
+      public void actionPerformed(ActionEvent e) {
+        somethingChanged();
+      }
+    });
   }
 
   @Override
@@ -103,6 +111,7 @@ public class PyCodeStylePanel extends CodeStyleAbstractPanel {
       }
     }
     myAddTrailingBlankLineCheckbox.setSelected(getCustomSettings(settings).BLANK_LINE_AT_FILE_END);
+    myUseContinuationIndentForArguments.setSelected(getCustomSettings(settings).USE_CONTINUATION_INDENT_FOR_ARGUMENTS);
   }
 
   @Override
@@ -110,6 +119,7 @@ public class PyCodeStylePanel extends CodeStyleAbstractPanel {
     final PyCodeStyleSettings customSettings = getCustomSettings(settings);
     customSettings.DICT_ALIGNMENT = getDictAlignmentAsInt();
     customSettings.BLANK_LINE_AT_FILE_END = ensureTrailingBlankLine();
+    customSettings.USE_CONTINUATION_INDENT_FOR_ARGUMENTS = useContinuationIndentForArguments();
   }
 
   @Override
@@ -137,8 +147,17 @@ public class PyCodeStylePanel extends CodeStyleAbstractPanel {
     return myAddTrailingBlankLineCheckbox.isSelected();
   }
 
-  public static final String PREVIEW = "{\n" +
-                                       "    \"green\": 42,\n" +
-                                       "    \"eggs and ham\": -0.0e0\n" +
-                                       "}";
+  private boolean useContinuationIndentForArguments() {
+    return myUseContinuationIndentForArguments.isSelected();
+  }
+
+  public static final String PREVIEW = "x = max(\n" +
+    "    1,\n" +
+    "    2,\n" +
+    "    3)\n" +
+    "\n" +
+    "{\n" +
+    "    \"green\": 42,\n" +
+    "    \"eggs and ham\": -0.0e0\n" +
+    "}";
 }

python/src/com/jetbrains/python/formatter/PyCodeStyleSettings.java

@@ -78,6 +78,14 @@ public class PyCodeStyleSettings extends CustomCodeStyleSettings {
   public boolean DICT_NEW_LINE_BEFORE_RIGHT_BRACE = false;
 
   public int BLANK_LINES_AFTER_LOCAL_IMPORTS = 0;
+  /**
+   * Code style for most languages use continuation indent both for parameters in function definition and for arguments in function calls.
+   * In Python continuation indent (assuming it's 8 spaces) for parameters is required by PEP 8, because otherwise they won't be visually 
+   * distinctive from function body. However for arguments (except several special cases) both normal and continuation indents are acceptable 
+   * (as long as they're multiple of 4), though examples in PEP 8 itself use mostly normal indent. Nontheless some users prefer to have 
+   * the same indetation level for arguments as for parameters.
+   */
+  public boolean USE_CONTINUATION_INDENT_FOR_ARGUMENTS = false;
 
   public PyCodeStyleSettings(CodeStyleSettings container) {
     super("Python", container);

python/testData/formatter/continuationIndentBeforeFunctionArguments.py

@@ -0,0 +1,10 @@
+sum(
+  1,
+    2, 3,
+5,
+)
+
+sum(
+1,
+         2, 3,
+  5)

python/testData/formatter/continuationIndentBeforeFunctionArguments_after.py

@@ -0,0 +1,10 @@
+sum(
+        1,
+        2, 3,
+        5,
+)
+
+sum(
+        1,
+        2, 3,
+        5)

python/testSrc/com/jetbrains/python/PyFormatterTest.java

@@ -659,4 +659,10 @@ public class PyFormatterTest extends PyTestCase {
   public void testBlanksBetweenImportsPreservedWithoutOptimizeImports() {
     doTest();
   }
+
+  // PY-17979, PY-13304
+  public void testContinuationIndentBeforeFunctionArguments() {
+    getPythonCodeStyleSettings().USE_CONTINUATION_INDENT_FOR_ARGUMENTS = true;
+    doTest();
+  }
 }