Add braceStyle option with same-line (default) and next-line choices.

src/options.ts

@@ -31,5 +31,21 @@ export default {
       { value: "end", description: "" }
     ],
     description: "Where to print operators when binary expressions wrap lines."
+  },
+  braceStyle: {
+    type: "choice",
+    category: "Java",
+    default: "same-line",
+    choices: [
+      {
+        value: "same-line",
+        description: "Put opening braces on same line (K&R style)"
+      },
+      {
+        value: "next-line",
+        description: "Put opening braces on new lines (Allman style)"
+      }
+    ],
+    description: "Placement of opening braces."
   }
 } satisfies SupportOptions;

src/printers/blocks-and-statements.ts

@@ -25,8 +25,8 @@ const {
 } = builders;
 
 export default {
-  block(path, print) {
-    return printBlock(path, printBlockStatements(path, print));
+  block(path, print, options) {
+    return printBlock(path, printBlockStatements(path, print), options);
   },
 
   local_variable_declaration: printVariableDeclaration,
@@ -47,7 +47,7 @@ export default {
       : [expression, ";"];
   },
 
-  if_statement(path, print) {
+  if_statement(path, print, options) {
     const statement = ["if ", path.call(print, "conditionNode")];
 
     if (path.node.consequenceNode.type === ";") {
@@ -63,6 +63,8 @@ export default {
     const danglingComments = printDanglingComments(path);
     if (danglingComments.length) {
       statement.push(hardline, ...danglingComments, hardline);
+    } else if (options?.braceStyle === "next-line") {
+      statement.push(hardline);
     } else {
       const ifHasBlock = path.node.consequenceNode.type === SyntaxType.Block;
       statement.push(ifHasBlock ? " " : hardline);
@@ -91,8 +93,8 @@ export default {
     ]);
   },
 
-  switch_block(path, print) {
-    return printBlock(path, path.map(print, "namedChildren"));
+  switch_block(path, print, options) {
+    return printBlock(path, path.map(print, "namedChildren"), options);
   },
 
   switch_block_statement_group(path, print) {
@@ -192,15 +194,16 @@ export default {
     }
   },
 
-  do_statement(path, print) {
+  do_statement(path, print, options) {
     const hasEmptyStatement = path.node.bodyNode.type === ";";
-    return [
-      "do",
-      hasEmptyStatement ? ";" : [" ", path.call(print, "bodyNode")],
-      " while ",
-      path.call(print, "conditionNode"),
-      ";"
-    ];
+    const isNextLine = options?.braceStyle === "next-line";
+    const whilePrefix = isNextLine ? [hardline, "while "] : " while ";
+    const body = hasEmptyStatement
+      ? ";"
+      : isNextLine
+        ? path.call(print, "bodyNode")
+        : [" ", path.call(print, "bodyNode")];
+    return ["do", body, whilePrefix, path.call(print, "conditionNode"), ";"];
   },
 
   for_statement(path, print) {
@@ -330,7 +333,7 @@ export default {
     ];
   },
 
-  try_statement(path, print) {
+  try_statement(path, print, options) {
     const parts = ["try", path.call(print, "bodyNode")];
 
     path.each(child => {
@@ -342,23 +345,26 @@ export default {
       }
     }, "namedChildren");
 
+    if (options?.braceStyle === "next-line") {
+      return parts;
+    }
     return join(" ", parts);
   },
 
-  catch_clause(path, print) {
+  catch_clause(path, print, options) {
     const catchFormalParameterIndex = path.node.namedChildren.findIndex(
       ({ type }) => type === SyntaxType.CatchFormalParameter
     );
-    return [
-      "catch ",
-      group(
-        indentInParentheses(
-          path.call(print, "namedChildren", catchFormalParameterIndex)
-        )
-      ),
-      " ",
-      path.call(print, "bodyNode")
-    ];
+    const params = group(
+      indentInParentheses(
+        path.call(print, "namedChildren", catchFormalParameterIndex)
+      )
+    );
+    const body = path.call(print, "bodyNode");
+    if (options?.braceStyle === "next-line") {
+      return [hardline, "catch ", params, body];
+    }
+    return ["catch ", params, " ", body];
   },
 
   catch_formal_parameter(path, print) {
@@ -383,27 +389,31 @@ export default {
     return join([line, "| "], path.map(print, "namedChildren"));
   },
 
-  finally_clause(path, print) {
+  finally_clause(path, print, options) {
+    if (options?.braceStyle === "next-line") {
+      return [hardline, "finally", path.call(print, "namedChildren", 0)];
+    }
     return ["finally ", path.call(print, "namedChildren", 0)];
   },
 
-  try_with_resources_statement(path, print) {
-    const parts = [
-      "try",
-      path.call(print, "resourcesNode"),
-      path.call(print, "bodyNode")
-    ];
+  try_with_resources_statement(path, print, options) {
+    const resources = path.call(print, "resourcesNode");
+    const body = path.call(print, "bodyNode");
+    const clauses: Doc[] = [];
 
     path.each(child => {
       if (
         child.node.type === SyntaxType.CatchClause ||
         child.node.type === SyntaxType.FinallyClause
       ) {
-        parts.push(print(child));
+        clauses.push(print(child));
       }
     }, "namedChildren");
 
-    return join(" ", parts);
+    if (options?.braceStyle === "next-line") {
+      return ["try ", resources, body, ...clauses];
+    }
+    return join(" ", ["try", resources, body, ...clauses]);
   },
 
   resource_specification(path, print) {

src/printers/classes.ts

@@ -19,7 +19,7 @@ const { group, hardline, indent, indentIfBreak, join, line, softline } =
   builders;
 
 export default {
-  class_declaration(path, print) {
+  class_declaration(path, print, options) {
     const parts: Doc[] = ["class ", path.call(print, "nameNode")];
     const definedClauses = definedKeys(path.node, [
       "superclassNode",
@@ -42,12 +42,14 @@ export default {
         hasChild(path, clause) ? [separator, path.call(print, clause)] : []
       );
       const hasBody = path.node.bodyNode.namedChildren.length > 0;
+      const afterClauses =
+        options?.braceStyle === "next-line" ? "" : hasBody ? separator : " ";
       const clauseGroup = [
         hasTypeParameters && !hasMultipleClauses ? clauses : indent(clauses),
-        hasBody ? separator : " "
+        afterClauses
       ];
       parts.push(hasMultipleClauses ? clauseGroup : group(clauseGroup));
-    } else {
+    } else if (options?.braceStyle !== "next-line") {
       parts.push(" ");
     }
 
@@ -89,14 +91,16 @@ export default {
     return join([",", line], path.map(print, "namedChildren"));
   },
 
-  class_body(path, print) {
+  class_body(path, print, options) {
     return printBlock(
       path,
       printBodyDeclarations(
         path,
         print,
-        (path.parent as NamedNode | null)?.type === SyntaxType.ClassDeclaration
-      )
+        (path.parent as NamedNode | null)?.type ===
+          SyntaxType.ClassDeclaration && options?.braceStyle !== "next-line"
+      ),
+      options
     );
   },
 
@@ -261,8 +265,8 @@ export default {
     return [modifiers, group(declaration), " ", path.call(print, "bodyNode")];
   },
 
-  constructor_body(path, print) {
-    return printBlock(path, printBlockStatements(path, print));
+  constructor_body(path, print, options) {
+    return printBlock(path, printBlockStatements(path, print), options);
   },
 
   explicit_constructor_invocation(path, print) {
@@ -379,7 +383,7 @@ export default {
     if (declarations.length) {
       contents.push(";", hardline, ...declarations);
     }
-    return printBlock(path, contents.length ? [contents] : []);
+    return printBlock(path, contents.length ? [contents] : [], options);
   },
 
   enum_constant(path, print) {

src/printers/helpers.ts

@@ -129,9 +129,22 @@ export function printArrayInitializer(
 ) {
   if (!path.node.namedChildren.length) {
     const danglingComments = printDanglingComments(path);
-    return danglingComments.length
-      ? ["{", indent([hardline, ...danglingComments]), hardline, "}"]
-      : "{}";
+    if (danglingComments.length) {
+      if (options.braceStyle === "next-line") {
+        const isNested =
+          path.parent?.type === SyntaxType.ArrayInitializer ||
+          path.parent?.type === SyntaxType.ElementValueArrayInitializer;
+        const block = [
+          "{",
+          indent([hardline, ...danglingComments]),
+          hardline,
+          "}"
+        ];
+        return isNested ? block : [hardline, ...block];
+      }
+      return ["{", indent([hardline, ...danglingComments]), hardline, "}"];
+    }
+    return "{}";
   }
 
   const list = join([",", line], path.map(print, "namedChildren"));
@@ -140,10 +153,26 @@ export function printArrayInitializer(
     list.push(ifBreak(","));
   }
 
+  if (options.braceStyle === "next-line") {
+    const isNested =
+      path.parent?.type === SyntaxType.ArrayInitializer ||
+      path.parent?.type === SyntaxType.ElementValueArrayInitializer;
+    const block = ["{", indent([softline, ...list]), softline, "}"];
+    return isNested ? block : [hardline, ...block];
+  }
+
   return group(["{", indent([softline, ...list]), softline, "}"]);
 }
 
-export function printBlock(path: NamedNodePath, contents: Doc[]) {
+export function printBlock(
+  path: NamedNodePath,
+  contents: Doc[],
+  options?: JavaParserOptions
+) {
+  if (options?.braceStyle === "next-line") {
+    return printBlockNextLine(path, contents);
+  }
+
   if (contents.length) {
     return group([
       "{",
@@ -195,6 +224,40 @@ export function printBlock(path: NamedNodePath, contents: Doc[]) {
     : ["{", hardline, "}"];
 }
 
+function printBlockNextLine(path: NamedNodePath, contents: Doc[]) {
+  const parentType = path.parent?.type;
+  const isChildOfBodyDeclaration =
+    parentType != null &&
+    [
+      SyntaxType.AnnotationTypeBody,
+      SyntaxType.ClassBody,
+      SyntaxType.EnumBody,
+      SyntaxType.InterfaceBody
+    ].includes(parentType);
+  const prefix = isChildOfBodyDeclaration ? [] : [hardline];
+
+  if (contents.length) {
+    return [
+      ...prefix,
+      "{",
+      indent([hardline, ...join(hardline, contents)]),
+      hardline,
+      "}"
+    ];
+  }
+  const danglingComments = printDanglingComments(path);
+  if (danglingComments.length) {
+    return [
+      ...prefix,
+      "{",
+      indent([hardline, ...danglingComments]),
+      hardline,
+      "}"
+    ];
+  }
+  return [...prefix, "{", hardline, "}"];
+}
+
 export function printBlockStatements(
   path: NamedNodePath<
     | SyntaxType.Block

src/printers/interfaces.ts

@@ -72,8 +72,8 @@ export default {
     ]);
   },
 
-  interface_body(path, print) {
-    return printBlock(path, printBodyDeclarations(path, print));
+  interface_body(path, print, options) {
+    return printBlock(path, printBodyDeclarations(path, print), options);
   },
 
   constant_declaration: printVariableDeclaration,
@@ -91,8 +91,8 @@ export default {
     return parts;
   },
 
-  annotation_type_body(path, print) {
-    return printBlock(path, printBodyDeclarations(path, print));
+  annotation_type_body(path, print, options) {
+    return printBlock(path, printBodyDeclarations(path, print), options);
   },
 
   annotation_type_element_declaration(path, print) {

src/printers/packages-and-modules.ts

@@ -134,7 +134,7 @@ export default {
     return join(" ", parts);
   },
 
-  module_body(path, print) {
+  module_body(path, print, options) {
     return printBlock(
       path,
       path.map(
@@ -143,7 +143,8 @@ export default {
             ? [hardline, print(child)]
             : print(child),
         "namedChildren"
-      )
+      ),
+      options
     );
   },
 

test/unit-test/braces-next-line/.prettierrc.json

@@ -0,0 +1 @@
+{ "braceStyle": "next-line" }