Fix what NullAway reports

Most of the 60 findings were a null the code meant, with no @nullable
where it went. Now marked @nullable:
- RawTok's and Tok's kind and string value, and a comment's text before
  it is first read;
- the parent of the root exploration node;
- the methods maybeGetMethod looks up, and the fields that keep them;
- the receiver of an unqualified call, and a dimension list's missing
  type;
- getLineEnding's result for a string without one;
- the three scan overrides, which javac calls with null for a missing
  tree.

Where a lookup cannot miss (a token at a position the input has, a
range the output built, a level's children), checkNotNull says so and
fails as the dereference did.

Besides that:
- variableFragmentDims no longer takes a missing type: its one caller
  that may have none maps the Optional instead.
- The javadoc lexer's newline after a `}` it moves has the "\n" of
  every other newline token rather than null. The formatter writes a
  line break for it and never reads the value.
- Newlines.LineIterator returns the line it reads instead of keeping it
  in a field.
- BootstrappingFormatterService runs the formatter without a working
  directory, rather than throwing, if the java binary has no parent
  directory.
- PalantirJavaFormatSettings.getState() is no longer @nullable: it
  never returns null.
- ParameterizedClass uses JUnit 6's computeIfAbsent, which never
  returns null, in place of the deprecated getOrComputeIfAbsent.
- FormatterIntegrationTest reads the expected output's line separator
  in the tests that use it.
- NullAway takes AssertJ's assertThat(x).isNotNull() in tests for the
  null check it is.

Author: abashev

buildSrc/src/main/groovy/open-java-format.error-prone-conventions.gradle

@@ -21,6 +21,9 @@ tasks.withType(JavaCompile).configureEach {
     options.errorprone {
         // Annotation processor output (Immutables) is not ours to fix.
         excludedPaths = '.*/build/generated/.*'
+        nullaway {
+            handleTestAssertionLibraries = true
+        }
         error('FormatStringConcatenation')
         error('JUnitClassModifiers')
         error('JUnitMethodDeclaration')

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/NativeImageAtomicCopyTest.java

@@ -45,8 +45,10 @@ void the_copy_is_executable_and_the_image_is_left_as_it_was() throws IOException
 
         var copy = NativeImageAtomicCopy.copyToCache(image, gradleUserHome.toFile());
 
-        assertThat(copy.getParent().getParent()).isEqualTo(gradleUserHome.resolve("open-java-format-caches"));
-        assertThat(copy.getParent().getFileName().toString()).matches("[0-9a-f]{16}");
+        var cacheDir = copy.getParent();
+        assertThat(cacheDir).isNotNull();
+        assertThat(cacheDir.getParent()).isEqualTo(gradleUserHome.resolve("open-java-format-caches"));
+        assertThat(cacheDir.getFileName().toString()).matches("[0-9a-f]{16}");
         assertThat(copy.getFileName()).isEqualTo(image.getFileName());
         assertThat(copy).hasContent("an image");
         assertThat(Files.isExecutable(copy)).isTrue();

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/PalantirJavaFormatFormattingService.java

@@ -65,6 +65,7 @@ Optional<PluginDescriptor> getPluginDescriptor() {
     }
 
     @Override
+    @Nullable
     protected FormattingTask createFormattingTask(AsyncFormattingRequest request) {
         Project project = request.getContext().getProject();
         // The marketplace verifier reports this class as experimental, and newer IDEs also deprecate it. It stays:

open-java-format-idea-plugin/src/main/java/com/palantir/javaformat/intellij/PalantirJavaFormatSettings.java

@@ -49,7 +49,6 @@ static PalantirJavaFormatSettings getInstance(Project project) {
     }
 
     @Override
-    @Nullable
     public StoredSettings getState() {
         return state;
     }
@@ -164,6 +163,7 @@ public void setImplementationClassPath(@Nullable List<String> value) {
                     .map(strings -> strings.stream().map(URI::create).collect(Collectors.toList()));
         }
 
+        @Nullable
         public List<String> getImplementationClassPath() {
             return implementationClassPath
                     .map(paths -> paths.stream().map(URI::toString).collect(Collectors.toList()))
@@ -181,6 +181,7 @@ public void setEnabled(@Nullable String enabledStr) {
             }
         }
 
+        @Nullable
         public String getEnabled() {
             return switch (enabled) {
                 case ENABLED -> "true";

open-java-format-idea-plugin/src/test/java/com/palantir/javaformat/intellij/PalantirJavaFormatFormattingServiceTest.java

@@ -48,6 +48,7 @@
 import java.nio.file.Paths;
 import java.util.List;
 
+import static java.util.Objects.requireNonNull;
 import static org.assertj.core.api.Assertions.assertThat;
 
 final class PalantirJavaFormatFormattingServiceTest {
@@ -126,10 +127,10 @@ private PsiFile createPsiFile(String path, String... contents) throws IOExceptio
 
     private static final class DelegatingFormatter extends PalantirJavaFormatFormattingService {
         public DelegatingFormatter() {
-            this.setPluginDescriptor(FormattingService.EP_NAME
-                    .findExtension(PalantirJavaFormatFormattingService.class)
-                    .getPluginDescriptor()
-                    .orElseThrow());
+            this.setPluginDescriptor(
+                    requireNonNull(FormattingService.EP_NAME.findExtension(PalantirJavaFormatFormattingService.class))
+                            .getPluginDescriptor()
+                            .orElseThrow());
         }
 
         private boolean invoked = false;
@@ -140,7 +141,7 @@ private boolean wasInvoked() {
 
         @Override
         protected FormattingTask createFormattingTask(AsyncFormattingRequest request) {
-            FormattingTask delegateTask = super.createFormattingTask(request);
+            FormattingTask delegateTask = requireNonNull(super.createFormattingTask(request));
             return new FormattingTask() {
                 @Override
                 public boolean cancel() {

open-java-format-jdk-bootstrap/src/main/java/com/palantir/javaformat/bootstrap/BootstrappingFormatterService.java

@@ -87,7 +87,7 @@ private ImmutableList<Replacement> getFormatReplacementsInternal(String input, C
                 ranges.stream().map(RangeUtils::toStringRange).collect(Collectors.toList()));
 
         Optional<String> output =
-                FormatterCommandRunner.runWithStdin(command.toArgs(), input, Optional.of(jdkPath.getParent()));
+                FormatterCommandRunner.runWithStdin(command.toArgs(), input, Optional.ofNullable(jdkPath.getParent()));
         if (output.isEmpty() || output.get().isEmpty()) {
             return ImmutableList.of();
         }

open-java-format/src/main/java/com/palantir/javaformat/Newlines.java

@@ -19,6 +19,7 @@
 import com.google.common.collect.Iterators;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
+import org.jspecify.annotations.Nullable;
 
 /** Platform-independent newline handling. */
 public class Newlines {
@@ -53,6 +54,7 @@ public static int hasNewlineAt(String input, int idx) {
     }
 
     /** Returns the terminating line break in the input, or {@code null} if the input does not end in a break. */
+    @Nullable
     public static String getLineEnding(String input) {
         for (String b : BREAKS) {
             if (input.endsWith(b)) {
@@ -154,7 +156,6 @@ public void remove() {
     private static final class LineIterator implements Iterator<String> {
 
         int idx;
-        String curr;
 
         private final String input;
         private final Iterator<Integer> indices;
@@ -165,7 +166,7 @@ private LineIterator(String input) {
             idx = indices.next(); // read leading 0
         }
 
-        private void advance() {
+        private String advance() {
             int last = idx;
             if (indices.hasNext()) {
                 idx = indices.next();
@@ -175,7 +176,7 @@ private void advance() {
             } else {
                 throw new NoSuchElementException();
             }
-            curr = input.substring(last, idx);
+            return input.substring(last, idx);
         }
 
         @Override
@@ -185,8 +186,7 @@ public boolean hasNext() {
 
         @Override
         public String next() {
-            advance();
-            return curr;
+            return advance();
         }
 
         @Override

open-java-format/src/main/java/com/palantir/javaformat/OpsBuilder.java

@@ -14,6 +14,8 @@
 
 package com.palantir.javaformat;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ArrayListMultimap;
@@ -49,14 +51,14 @@ public final class OpsBuilder {
 
     /** Return the actual size of the AST node at position, including comments. */
     public int actualSize(int position, int length) {
-        Input.Token startToken = input.getPositionTokenMap().get(position);
+        Input.Token startToken = checkNotNull(input.getPositionTokenMap().get(position));
         int start = startToken.getTok().getPosition();
         for (Input.Tok tok : startToken.getToksBefore()) {
             if (tok.isComment()) {
                 start = Math.min(start, tok.getPosition());
             }
         }
-        Input.Token endToken = input.getPositionTokenMap().get(position + length - 1);
+        Input.Token endToken = checkNotNull(input.getPositionTokenMap().get(position + length - 1));
         int end = endToken.getTok().getPosition() + endToken.getTok().length();
         for (Input.Tok tok : endToken.getToksAfter()) {
             if (tok.isComment()) {
@@ -68,7 +70,7 @@ public int actualSize(int position, int length) {
 
     /** Return the start column of the token at {@code position}, including leading comments. */
     public Integer actualStartColumn(int position) {
-        Input.Token startToken = input.getPositionTokenMap().get(position);
+        Input.Token startToken = checkNotNull(input.getPositionTokenMap().get(position));
         int start = startToken.getTok().getPosition();
         int line0 = input.getLineNumber(start);
         for (Input.Tok tok : startToken.getToksBefore()) {

open-java-format/src/main/java/com/palantir/javaformat/doc/Obs.java

@@ -20,6 +20,7 @@
 import java.util.Optional;
 import java.util.OptionalInt;
 import java.util.function.Function;
+import org.jspecify.annotations.Nullable;
 
 /**
  * These classes exist purely for observing the operation of {@link Doc#computeBreaks}, including all the alternative
@@ -170,7 +171,7 @@ private static class ExplorationNodeImpl extends HasUniqueId implements Explorat
         private final Optional<Level> parentLevel;
 
         public ExplorationNodeImpl(
-                LevelNodeImpl parent,
+                @Nullable LevelNodeImpl parent,
                 String humanDescription,
                 Sink sink,
                 int startColumn,

open-java-format/src/main/java/com/palantir/javaformat/java/CommandLineOptionsParser.java

@@ -107,7 +107,7 @@ static CommandLineOptions parse(Iterable<String> options) {
         return optionsBuilder.build();
     }
 
-    private static Integer parseInteger(Iterator<String> it, String flag, String value) {
+    private static Integer parseInteger(Iterator<String> it, String flag, @Nullable String value) {
         try {
             return Integer.valueOf(getValue(flag, it, value));
         } catch (NumberFormatException e) {