Add a layout solver to google-java-format based on Wadler's prettier printer.

core/src/main/java/com/google/googlejavaformat/Doc.java

@@ -365,7 +365,7 @@ public enum RealOrImaginary {
       REAL,
       IMAGINARY;
 
-      boolean isReal() {
+      public boolean isReal() {
         return this == REAL;
       }
     }
@@ -395,12 +395,12 @@ private Token(
      *
      * @return the extra indent
      */
-    Indent getPlusIndentCommentsBefore() {
+    public Indent getPlusIndentCommentsBefore() {
       return plusIndentCommentsBefore;
     }
 
     /** Force a line break and indent trailing javadoc or block comments. */
-    Optional<Indent> breakAndIndentTrailingComment() {
+    public Optional<Indent> breakAndIndentTrailingComment() {
       return breakAndIndentTrailingComment;
     }
 
@@ -427,7 +427,7 @@ static Op make(
      *
      * @return the {@link Input.Token}
      */
-    Input.Token getToken() {
+    public Input.Token getToken() {
       return token;
     }
 
@@ -436,7 +436,7 @@ Input.Token getToken() {
      *
      * @return whether the @code Token} is good
      */
-    RealOrImaginary realOrImaginary() {
+    public RealOrImaginary realOrImaginary() {
       return realOrImaginary;
     }
 
@@ -483,7 +483,7 @@ public String toString() {
   }
 
   /** A Leaf node in a {@link Doc} for a non-breaking space. */
-  static final class Space extends Doc implements Op {
+  public static final class Space extends Doc implements Op {
     private static final Space SPACE = new Space();
 
     private Space() {}
@@ -600,6 +600,22 @@ boolean isForced() {
       return fillMode == FillMode.FORCED;
     }
 
+    public FillMode fillMode() {
+      return fillMode;
+    }
+
+    public String flat() {
+      return flat;
+    }
+
+    public Indent plusIndent() {
+      return plusIndent;
+    }
+
+    public Optional<BreakTag> optTag() {
+      return optTag;
+    }
+
     @Override
     public void add(DocBuilder builder) {
       builder.breakDoc(this);

core/src/main/java/com/google/googlejavaformat/Indent.java

@@ -24,7 +24,7 @@
  */
 public abstract class Indent {
 
-  abstract int eval();
+  public abstract int eval();
 
   /** A constant function, returning a constant indent. */
   public static final class Const extends Indent {
@@ -41,7 +41,7 @@ public static Const make(int n, int indentMultiplier) {
     }
 
     @Override
-    int eval() {
+    public int eval() {
       return n;
     }
 
@@ -68,7 +68,7 @@ public static If make(BreakTag condition, Indent thenIndent, Indent elseIndent)
     }
 
     @Override
-    int eval() {
+    public int eval() {
       return (condition.wasBreakTaken() ? thenIndent : elseIndent).eval();
     }
 

core/src/main/java/com/google/googlejavaformat/Newlines.java

@@ -35,6 +35,21 @@ public static int firstBreak(String input) {
     return it.hasNext() ? it.next() : -1;
   }
 
+  /**
+   * Returns the offset of the start of the last line in the input, or {@code 0} if the input
+   * contains no line breaks. Unlike iterating over {@link #lineOffsetIterator}, this only scans the
+   * last line.
+   */
+  public static int lastLineStart(String input) {
+    for (int i = input.length() - 1; i >= 0; i--) {
+      char c = input.charAt(i);
+      if (c == '\n' || c == '\r') {
+        return i + 1;
+      }
+    }
+    return 0;
+  }
+
   private static final ImmutableSet<String> BREAKS = ImmutableSet.of("\r\n", "\n", "\r");
 
   /** Returns true if the entire input string is a recognized line break. */

core/src/main/java/com/google/googlejavaformat/OpenOp.java

@@ -44,6 +44,10 @@ public void add(DocBuilder builder) {
     builder.open(plusIndent);
   }
 
+  public Indent plusIndent() {
+    return plusIndent;
+  }
+
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this).add("plusIndent", plusIndent).toString();

core/src/main/java/com/google/googlejavaformat/java/Formatter.java

@@ -25,11 +25,11 @@
 import com.google.errorprone.annotations.Immutable;
 import com.google.googlejavaformat.CommentsHelper;
 import com.google.googlejavaformat.Doc;
-import com.google.googlejavaformat.DocBuilder;
 import com.google.googlejavaformat.FormattingError;
 import com.google.googlejavaformat.Newlines;
 import com.google.googlejavaformat.Op;
-import com.google.googlejavaformat.OpsBuilder;
+import com.google.googlejavaformat.layout.LayoutBuilder;
+import com.google.googlejavaformat.layout.LayoutSolver;
 import com.sun.tools.javac.tree.JCTree.JCCompilationUnit;
 import com.sun.tools.javac.util.Context;
 import java.io.IOException;
@@ -113,22 +113,21 @@ static void format(final JavaInput javaInput, JavaOutput javaOutput, JavaFormatt
     if (!errorDiagnostics.isEmpty()) {
       throw FormatterException.fromJavacDiagnostics(errorDiagnostics);
     }
-    OpsBuilder builder = new OpsBuilder(javaInput, javaOutput);
+    LayoutBuilder builder = new LayoutBuilder(javaInput, javaOutput);
     ImmutableSet.Builder<Integer> markdownJavadocPositions = ImmutableSet.builder();
     // Output the compilation unit.
     JavaInputAstVisitor visitor =
         new JavaInputAstVisitor(builder, options.indentationMultiplier(), markdownJavadocPositions);
     visitor.scan(unit, null);
     builder.sync(javaInput.getText().length());
     builder.drain();
-    Doc doc = new DocBuilder().withOps(builder.build()).build();
+    var doc = builder.build();
     CommentsHelper commentsHelper =
         new JavaCommentsHelper(
             Newlines.guessLineSeparator(javaInput.getText()),
             options,
             markdownJavadocPositions.build());
-    doc.computeBreaks(commentsHelper, options.maxLineLength(), new Doc.State(+0, 0));
-    doc.write(javaOutput);
+    LayoutSolver.format(doc, options.maxLineLength(), javaOutput, commentsHelper);
     javaOutput.flush();
   }
 

core/src/main/java/com/google/googlejavaformat/java/JavaInputAstVisitor.java

@@ -78,11 +78,11 @@
 import com.google.googlejavaformat.Newlines;
 import com.google.googlejavaformat.Op;
 import com.google.googlejavaformat.OpenOp;
-import com.google.googlejavaformat.OpsBuilder;
 import com.google.googlejavaformat.OpsBuilder.BlankLineWanted;
 import com.google.googlejavaformat.Output.BreakTag;
 import com.google.googlejavaformat.java.DimensionHelpers.SortedDims;
 import com.google.googlejavaformat.java.DimensionHelpers.TypeWithDims;
+import com.google.googlejavaformat.layout.LayoutBuilder;
 import com.sun.source.tree.AnnotatedTypeTree;
 import com.sun.source.tree.AnnotationTree;
 import com.sun.source.tree.ArrayAccessTree;
@@ -272,7 +272,7 @@
     return result.build();
   }
 
-  private final OpsBuilder builder;
+  private final LayoutBuilder builder;
   private final ImmutableSet.Builder<Integer> markdownJavadocPositions;
 
   private static final Indent.Const ZERO = Indent.Const.ZERO;
@@ -308,10 +308,10 @@
   /**
    * The {@code Visitor} constructor.
    *
-   * @param builder the {@link OpsBuilder}
+   * @param builder the {@link LayoutBuilder}
    */
   JavaInputAstVisitor(
-      OpsBuilder builder,
+      LayoutBuilder builder,
       int indentMultiplier,
       ImmutableSet.Builder<Integer> markdownJavadocPositions) {
     this.builder = builder;
@@ -529,7 +529,7 @@
         if (afterFirstToken) {
           builder.forcedBreak();
         }
         builder.open(row.iterator().next().getKind() == NEW_ARRAY || cols == 1 ? ZERO : plusFour);
         boolean firstInRow = true;
         for (ExpressionTree item : row) {
           if (!firstInRow) {
@@ -769,7 +769,7 @@
         CollapseEmptyOrNot.YES,
         AllowLeadingBlankLine.YES,
         AllowTrailingBlankLine.YES);
     if (node.getStatement().getKind() == BLOCK) {
       builder.space();
     } else {
       builder.breakOp(" ");
@@ -1085,11 +1085,11 @@
     builder.open(plusFour);
     builder.open(
         node.getInitializer().size() > 1
                 && node.getInitializer().get(0).getKind() == Tree.Kind.EXPRESSION_STATEMENT
             ? plusFour
             : ZERO);
     if (!node.getInitializer().isEmpty()) {
       if (node.getInitializer().get(0).getKind() == VARIABLE) {
         PeekingIterator<StatementTree> it =
             Iterators.peekingIterator(node.getInitializer().iterator());
         visitVariables(
@@ -1153,7 +1153,7 @@
     while (true) {
       expressions.add(node.getCondition());
       statements.add(node.getThenStatement());
       if (node.getElseStatement() != null && node.getElseStatement().getKind() == IF) {
         node = (IfTree) node.getElseStatement();
       } else {
         break;
@@ -2998,7 +2998,7 @@
     builder.close();
   }
 
   /** Collapse chains of {@code .} operators, across multiple {@link ASTNode} types. */
 
   /**
    * Output a "." node.