Add --style to select the formatting style

--aosp was the only style switch, with no way to select Google Style once it had
been passed. Wrapper scripts such as Chromium's google-java-format launcher
append --aosp unconditionally, leaving projects that format through them no way
to opt back into Google Style.

Add a --style=<google|aosp> flag, and allow overriding a previously given style.
--aosp is kept as an alias for --style=aosp.

Author: hferreiro

README.md

@@ -27,7 +27,7 @@ offsets (`--offset`), passing through to standard-out (default) or altered
 in-place (`--replace`).
 
 Option `--help` will print full usage details; including built-in documentation
-about other flags, such as `--aosp`, `--fix-imports-only`,
+about other flags, such as `--style`, `--fix-imports-only`,
 `--skip-sorting-imports`, `--skip-removing-unused-import`,
 `--skip-reflowing-long-strings`, `--skip-javadoc-formatting`, or the `--dry-run`
 and `--set-exit-if-changed`.

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

@@ -18,6 +18,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableRangeSet;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
+import com.google.googlejavaformat.java.JavaFormatterOptions.Style;
 import java.util.Optional;
 
 /**
@@ -28,7 +29,7 @@
  * @param lines Line ranges to format.
  * @param offsets Character offsets for partial formatting, paired with {@code lengths}.
  * @param lengths Partial formatting region lengths, paired with {@code offsets}.
- * @param aosp Use AOSP style instead of Google Style (4-space indentation).
+ * @param style The style to format with.
  * @param version Print the version.
  * @param help Print usage information.
  * @param stdin Format input from stdin.
@@ -47,7 +48,7 @@ record CommandLineOptions(
     ImmutableRangeSet<Integer> lines,
     ImmutableList<Integer> offsets,
     ImmutableList<Integer> lengths,
-    boolean aosp,
+    Style style,
     boolean version,
     boolean help,
     boolean stdin,
@@ -73,7 +74,7 @@ static Builder builder() {
         .reflowLongStrings(true)
         .formatJavadoc(true)
         .reorderModifiers(true)
-        .aosp(false)
+        .style(Style.GOOGLE)
         .version(false)
         .help(false)
         .stdin(false)
@@ -108,7 +109,7 @@ default Builder addLength(Integer length) {
       return this;
     }
 
-    Builder aosp(boolean aosp);
+    Builder style(Style style);
 
     Builder version(boolean version);
 

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

@@ -16,12 +16,14 @@
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 
+import com.google.common.base.Ascii;
 import com.google.common.base.CharMatcher;
 import com.google.common.base.Splitter;
 import com.google.common.collect.ImmutableRangeSet;
 import com.google.common.collect.Range;
 import com.google.common.collect.RangeSet;
 import com.google.common.collect.TreeRangeSet;
+import com.google.googlejavaformat.java.JavaFormatterOptions.Style;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.nio.file.Files;
@@ -71,7 +73,9 @@ static CommandLineOptions parse(Iterable<String> options) {
             parseRangeSet(linesBuilder, getValue(flag, it, value));
         case "--offset", "-offset" -> optionsBuilder.addOffset(parseInteger(it, flag, value));
         case "--length", "-length" -> optionsBuilder.addLength(parseInteger(it, flag, value));
-        case "--aosp", "-aosp", "-a" -> optionsBuilder.aosp(true);
+        case "--style", "-style" ->
+            optionsBuilder.style(parseStyle(flag, getValue(flag, it, value)));
+        case "--aosp", "-aosp", "-a" -> optionsBuilder.style(Style.AOSP);
         case "--version", "-version", "-v" -> optionsBuilder.version(true);
         case "--help", "-help", "-h" -> optionsBuilder.help(true);
         case "--fix-imports-only" -> optionsBuilder.fixImportsOnly(true);
@@ -92,6 +96,16 @@ static CommandLineOptions parse(Iterable<String> options) {
     return optionsBuilder.build();
   }
 
+  private static Style parseStyle(String flag, String value) {
+    return switch (Ascii.toLowerCase(value)) {
+      case "google" -> Style.GOOGLE;
+      case "aosp" -> Style.AOSP;
+      default ->
+          throw new IllegalArgumentException(
+              String.format("invalid value for %s: %s (expected google or aosp)", flag, value));
+    };
+  }
+
   private static Integer parseInteger(Iterator<String> it, String flag, String value) {
     try {
       return Integer.valueOf(getValue(flag, it, value));

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

@@ -20,7 +20,6 @@
 
 import com.google.common.io.ByteStreams;
 import com.google.common.util.concurrent.MoreExecutors;
-import com.google.googlejavaformat.java.JavaFormatterOptions.Style;
 import java.io.IOError;
 import java.io.IOException;
 import java.io.InputStream;
@@ -118,7 +117,7 @@ public int format(String... args) throws UsageException {
 
     JavaFormatterOptions options =
         JavaFormatterOptions.builder()
-            .style(parameters.aosp() ? Style.AOSP : Style.GOOGLE)
+            .style(parameters.style())
             .formatJavadoc(parameters.formatJavadoc())
             .reorderModifiers(parameters.reorderModifiers())
             .build();

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

@@ -34,8 +34,11 @@ final class UsageException extends Exception {
     Format stdin -> stdout
   --assume-filename, -assume-filename
     File name to use for diagnostics when formatting standard input (default is <stdin>).
+  --style, -style
+    The style to format with, either google (2-space indentation) or aosp (4-space
+    indentation). The default is google; if given more than once, the last one wins.
   --aosp, -aosp, -a
-    Use AOSP style instead of Google Style (4-space indentation).
+    Alias for --style=aosp.
   --fix-imports-only
     Fix import order and remove any unused imports, but do no other formatting.
   --skip-sorting-imports

core/src/test/java/com/google/googlejavaformat/java/CommandLineOptionsParserTest.java

@@ -16,9 +16,11 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.junit.Assert.assertThrows;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Range;
+import com.google.googlejavaformat.java.JavaFormatterOptions.Style;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -40,7 +42,7 @@ public void defaults() {
     CommandLineOptions options = CommandLineOptionsParser.parse(ImmutableList.of());
     assertThat(options.files()).isEmpty();
     assertThat(options.stdin()).isFalse();
-    assertThat(options.aosp()).isFalse();
+    assertThat(options.style()).isEqualTo(Style.GOOGLE);
     assertThat(options.help()).isFalse();
     assertThat(options.lengths()).isEmpty();
     assertThat(options.lines().asRanges()).isEmpty();
@@ -74,7 +76,41 @@ public void stdin() {
 
   @Test
   public void aosp() {
-    assertThat(CommandLineOptionsParser.parse(Arrays.asList("-aosp")).aosp()).isTrue();
+    assertThat(CommandLineOptionsParser.parse(Arrays.asList("-aosp")).style())
+        .isEqualTo(Style.AOSP);
+  }
+
+  @Test
+  public void style() {
+    assertThat(CommandLineOptionsParser.parse(Arrays.asList("--style=google")).style())
+        .isEqualTo(Style.GOOGLE);
+    assertThat(CommandLineOptionsParser.parse(Arrays.asList("--style", "aosp")).style())
+        .isEqualTo(Style.AOSP);
+    assertThat(CommandLineOptionsParser.parse(Arrays.asList("-style=AOSP")).style())
+        .isEqualTo(Style.AOSP);
+  }
+
+  @Test
+  public void lastStyleWins() {
+    assertThat(CommandLineOptionsParser.parse(Arrays.asList("--aosp", "--style=google")).style())
+        .isEqualTo(Style.GOOGLE);
+    assertThat(CommandLineOptionsParser.parse(Arrays.asList("--style=google", "--aosp")).style())
+        .isEqualTo(Style.AOSP);
+    assertThat(
+            CommandLineOptionsParser.parse(Arrays.asList("--style=google", "--style=aosp")).style())
+        .isEqualTo(Style.AOSP);
+    assertThat(
+            CommandLineOptionsParser.parse(Arrays.asList("--style=aosp", "--style=google")).style())
+        .isEqualTo(Style.GOOGLE);
+  }
+
+  @Test
+  public void unknownStyle() {
+    IllegalArgumentException e =
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> CommandLineOptionsParser.parse(Arrays.asList("--style=llvm")));
+    assertThat(e).hasMessageThat().contains("invalid value for --style: llvm");
   }
 
   @Test