Make padded cell mandatory

PADDEDCELL.md

@@ -31,26 +31,7 @@ The rule we wrote above is obviously a bad idea.  But complex code formatters ca
 
 Formally, a correct formatter `F` must satisfy `F(F(input)) == F(input)` for all values of input.  Any formatter which doesn't meet this rule is misbehaving.
 
-## How does `paddedCell()` work?
-
-Spotless now has a special `paddedCell()` mode.  If you add it to your format as such:
-
-```gradle
-spotless {
-  format 'cpp', {
-    ...
-    paddedCell()
-  }
-}
-```
-
-then it will run in the following way:
-
-- When you call `spotlessApply`, it will automatically check for a ping-pong condition.
-- If there is a ping-pong condition, it will resolve the ambiguity arbitrarily, but consistently
-- It will also warn that `filename such-and-such cycles between 2 steps`.
-
-## How is the ambiguity resolved?
+## How spotless fixes this automatically
 
 This is easiest to show in an example:
 

lib/src/main/java/com/diffplug/spotless/PaddedCell.java

@@ -20,6 +20,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Files;
+import java.nio.file.StandardOpenOption;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -28,6 +29,8 @@
 import java.util.Objects;
 import java.util.function.Function;
 
+import org.omg.CORBA.portable.OutputStream;
+
 /**
  * Models the result of applying a {@link Formatter} on a given {@link File}
  * while characterizing various failure modes (slow convergence, cycles, and divergence).
@@ -227,7 +230,7 @@ public static DirtyState calculateDirtyState(Formatter formatter, File file) thr
 	 * - {@link #isClean()} means that the file is is clean, and there's nothing else to say
 	 * - {@link #isConverged()} means that we were able to determine a clean state
 	 * - once you've tested the above conditions and you know that it's a dirty file with a converged state,
-	 *   then you can call {@link #canonicalBytes()} to get the canonical form of the given file.
+	 *   then you can call {@link #writeCanonicalTo()} to get the canonical form of the given file.
 	 */
 	public static class DirtyState {
 		private final byte[] canonicalBytes;
@@ -244,8 +247,19 @@ public boolean didNotConverge() {
 			return this == didNotConverge;
 		}
 
-		public byte[] canonicalBytes() {
-			return Objects.requireNonNull(canonicalBytes, "First make sure that `!isClean()` and `!didNotConverge()`");
+		private byte[] canonicalBytes() {
+			if (canonicalBytes == null) {
+				throw new IllegalStateException("First make sure that `!isClean()` and `!didNotConverge()`");
+			}
+			return canonicalBytes;
+		}
+
+		public void writeCanonicalTo(File file) throws IOException {
+			Files.write(file.toPath(), canonicalBytes(), StandardOpenOption.TRUNCATE_EXISTING);
+		}
+
+		public void writeCanonicalTo(OutputStream out) throws IOException {
+			out.write(canonicalBytes());
 		}
 	}
 

lib/src/main/java/com/diffplug/spotless/PaddedCellBulk.java

@@ -22,7 +22,6 @@
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.nio.file.SimpleFileVisitor;
-import java.nio.file.StandardOpenOption;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -186,7 +185,7 @@ public static boolean applyAnyChanged(Formatter formatter, File file) throws IOE
 		if (dirtyState.isClean() || dirtyState.didNotConverge()) {
 			return false;
 		} else {
-			Files.write(file.toPath(), dirtyState.canonicalBytes(), StandardOpenOption.TRUNCATE_EXISTING);
+			dirtyState.writeCanonicalTo(file);
 			return true;
 		}
 	}

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTask.java

@@ -18,8 +18,6 @@
 import java.io.File;
 import java.io.Serializable;
 import java.nio.charset.Charset;
-import java.nio.file.Files;
-import java.nio.file.StandardOpenOption;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -272,7 +270,7 @@ private List<File> applyAnyChanged(Formatter formatter, List<File> outOfDate) th
 			} else if (dirtyState.didNotConverge()) {
 				getLogger().warn("Skipping '" + file + "' because it does not converge.  Run `spotlessDiagnose` to understand why");
 			} else {
-				Files.write(file.toPath(), dirtyState.canonicalBytes(), StandardOpenOption.TRUNCATE_EXISTING);
+				dirtyState.writeCanonicalTo(file);
 				changed.add(file);
 			}
 		}