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Extension Settings

The vscode-antlr4 extension can be configured in many ways to support your preferred working style. Below is a grouped list of all currently supported settings.


  • antlr4.referencesCodeLens.enabled, boolean (default: false), if true enables the reference count display via Code Lens
  • antlr4.customcss, array of string (no default), list of absolute CSS file names for diagrams/graphs
  • antlr4.rrd.saveDir, string (no default), default export target folder for railroad (syntax) diagrams
  •, string (no default), default export target folder for call graphs
  • antlr4.atn.saveDir, string (no default), default export target folder for atn graph
  • antlr4.atn.maxLabelCount, number (default: 3), max number of labels displayed on a transition in an ATN graph

Parser Generation

This is a settings object named antlr4.generation with the following members:

  • mode, string enum (default: "internal"), determines what code generation pattern should be followed:
    • none: don't generate any code, not even for internal use (note: this value will disable grammar debugging)
    • internal: allow code generation for internal use (e.g. for full error detection and interpreter data)
    • external: generate code also for external use, depending on the other generation options
  • outputDir, string (default: undefined), determines the output folder where to place generated code (considered only if mode is set to external)
  • importDir, string (default: undefined), location to import grammars from (relative to the grammar that is being saved, or an absolute path), used also for internal code generation
  • package, string (default: undefined), package/namespace for generated code (used only in external mode)
  • language, string (default: "Java"), specifies the target language for the generated code, overriding what is specified in the grammar (used only in external mode)
  • listeners, boolean (default: true), also create listeners on code generation (used only in external mode)
  • visitors, boolean (default: false), also create visitors on code generation (used only in external mode)

Grammar Formatting

This is a settings object named antlr4.format with the following members:

  • alignTrailingComments: boolean (default: false), if true, aligns trailing comments
  • allowShortBlocksOnASingleLine: boolean (default: true), allows contracting short blocks to a single line
  • breakBeforeBraces: boolean (default: false), when true start predicates and actions on a new line
  • columnLimit: number (default: 100), the character count after which automatic line breaking takes place
  • continuationIndentWidth: number (default: 4), indentation for line continuation (only used if useTab is false)
  • indentWidth: number (default: 4), character count for indentation (if useTab is false)
  • keepEmptyLinesAtTheStartOfBlocks: boolean (default: false), if true, empty lines at the start of blocks are kept
  • maxEmptyLinesToKeep: number (default: 1), the maximum number of consecutive empty lines to keep
  • reflowComments: boolean (default: true), reformat comments to fit the column limit
  • spaceBeforeAssignmentOperators: boolean (default: true), enables spaces around operators
  • tabWidth: number (default: 4), multiples of this value determine tab stops in a document
  • useTab: boolean (default: true), use tabs for indentation (otherwise spaces)
  • alignColons: string enum (default: "none"), align colons among rules (scope depends on groupedAlignments)
    • none: place the colon directly after the rule name
    • trailing: align colons in the alignment group, directly after rule names
    • hanging: align the colon on the next line (with the pipe chars)
  • singleLineOverrulesHangingColon: boolean (default: true), single line mode overrides hanging colon setting (applies also to alignSemicolons)
  • allowShortRulesOnASingleLine: boolean (default: true), allows contracting short rules on a single line (short: < 2/3 of columnLimit)
  • alignSemicolons: string enum (default: "none"), determines the alignment of semicolons in rules
    • none: no alignment, just put it at the end of the rule directly after the last token
    • ownLine: put it on an own line (not indented), unless allowShortRulesOnASingleLine kicks in
    • hanging: put it on an own line with indentation (aligning it so to the alt pipe chars)
  • breakBeforeParens: boolean (default: false), for blocks: if true puts opening parentheses on an own line
  • ruleInternalsOnSingleLine: boolean (default: false), place rule internals (return value, local variables, @init, @after) all on a single line
  • minEmptyLines: number (default: 0), determines the number of empty lines that must exist (between rules or other full statements)
  • groupedAlignments: boolean (default: true), when true only consecutive lines are considered for alignments
  • alignFirstTokens: boolean (default: false), align the first token after the colon among rules
  • alignLexerCommands: boolean (default: false), align lexer commands (starting with ->) among rules
  • alignActions: boolean (default: false), align action blocks + predicates among rules and alternatives
  • alignLabels: boolean (default: true), align alt labels (only when a rule is not on a single line)
  • alignTrailers: boolean (default: false), combine all alignments (align whatever comes first: colons, comments etc.)


This is a settings object named antlr4.debug with the following members:

  • visualParseTreeHorizontal: boolean (default: true) Determines if parse trees by default use the horizontal layout (when true) or the vertical orientation (when false).
  • visualParseTreeClustered: boolean (default: false) When set to true parse trees will align their terminal nodes on a single row or column (depending on the orientation).
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