IntelliJ Platform Plugin SDK Help

16. Formatter

The IntelliJ Platform includes a powerful framework for implementing formatting for custom languages. A formatter enables reformatting code automatically based on code style settings. The formatter controls spaces, indents, wrap, and alignment.

Define a Block

The formatting model represents the formatting structure of a file as a tree of Block objects, with associated indent, wrap, alignment and spacing settings. The goal is to cover each PSI element with such a block. Since each block builds its children's blocks, it can generate extra blocks or skip any PSI elements. Define SimpleBlock based on AbstractBlock.

public class SimpleBlock extends AbstractBlock { private final SpacingBuilder spacingBuilder; protected SimpleBlock(@NotNull ASTNode node, @Nullable Wrap wrap, @Nullable Alignment alignment, SpacingBuilder spacingBuilder) { super(node, wrap, alignment); this.spacingBuilder = spacingBuilder; } @Override protected List<Block> buildChildren() { List<Block> blocks = new ArrayList<>(); ASTNode child = myNode.getFirstChildNode(); while (child != null) { if (child.getElementType() != TokenType.WHITE_SPACE) { Block block = new SimpleBlock(child, Wrap.createWrap(WrapType.NONE, false), Alignment.createAlignment(), spacingBuilder); blocks.add(block); } child = child.getTreeNext(); } return blocks; } @Override public Indent getIndent() { return Indent.getNoneIndent(); } @Nullable @Override public Spacing getSpacing(@Nullable Block child1, @NotNull Block child2) { return spacingBuilder.getSpacing(this, child1, child2); } @Override public boolean isLeaf() { return myNode.getFirstChildNode() == null; } }

Define a Formatting Model Builder

Define a formatter that removes extra spaces except for the single spaces around the property separator:

foo = bar
foo = bar

Create SimpleFormattingModelBuilder by implementing FormattingModelBuilder.

public class SimpleFormattingModelBuilder implements FormattingModelBuilder { private static SpacingBuilder createSpaceBuilder(CodeStyleSettings settings) { return new SpacingBuilder(settings, SimpleLanguage.INSTANCE) .around(SimpleTypes.SEPARATOR) .spaceIf(settings.getCommonSettings(SimpleLanguage.INSTANCE.getID()).SPACE_AROUND_ASSIGNMENT_OPERATORS) .before(SimpleTypes.PROPERTY) .none(); } @Override public @NotNull FormattingModel createModel(@NotNull FormattingContext formattingContext) { final CodeStyleSettings codeStyleSettings = formattingContext.getCodeStyleSettings(); return FormattingModelProvider .createFormattingModelForPsiFile(formattingContext.getContainingFile(), new SimpleBlock(formattingContext.getNode(), Wrap.createWrap(WrapType.NONE, false), Alignment.createAlignment(), createSpaceBuilder(codeStyleSettings)), codeStyleSettings); } }

Register the Formatter

The SimpleFormattingModelBuilder implementation is registered with the IntelliJ Platform in the plugin configuration file using the com.intellij.lang.formatter extension point.

<extensions defaultExtensionNs="com.intellij"> <lang.formatter language="Simple" implementationClass="org.intellij.sdk.language.SimpleFormattingModelBuilder"/> </extensions>

Run the Project

Run the plugin by using the Gradle runIde task.

Open the example Simple Language properties file in the IDE Development Instance. Add some extra spaces around the = separator between language and English. Reformat the code by invoking Code | Reformat File... dialog and choose Run.

Last modified: 27 February 2023