Add @Nullable annotations and NullAway profile for Maven 4 API

api/maven-api-annotations/src/main/java/org/apache/maven/api/annotations/Nullable.java

@@ -19,8 +19,10 @@
 package org.apache.maven.api.annotations;
 
 import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
 
 /**
  * The annotated element can be {@code null}.
@@ -31,4 +33,5 @@
 @Experimental
 @Documented
 @Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD})
 public @interface Nullable {}

api/maven-api-cli/src/main/java/org/apache/maven/api/cli/ParserRequest.java

@@ -279,12 +279,25 @@ class Builder {
 
         private final Logger logger;
         private Lookup lookup = EMPTY_LOOKUP;
+
+        @Nullable
         private Path cwd;
+
+        @Nullable
         private Path mavenHome;
+
+        @Nullable
         private Path userHome;
+
+        @Nullable
         private InputStream stdIn;
+
+        @Nullable
         private OutputStream stdOut;
+
+        @Nullable
         private OutputStream stdErr;
+
         private boolean embedded = false;
 
         private Builder(
@@ -361,12 +374,25 @@ private static class ParserRequestImpl implements ParserRequest {
             private final MessageBuilderFactory messageBuilderFactory;
             private final List<String> args;
             private final Lookup lookup;
+
+            @Nullable
             private final Path cwd;
+
+            @Nullable
             private final Path mavenHome;
+
+            @Nullable
             private final Path userHome;
+
+            @Nullable
             private final InputStream stdIn;
+
+            @Nullable
             private final OutputStream stdOut;
+
+            @Nullable
             private final OutputStream stdErr;
+
             private final boolean embedded;
 
             private ParserRequestImpl(
@@ -376,12 +402,12 @@ private ParserRequestImpl(
                     Logger logger,
                     MessageBuilderFactory messageBuilderFactory,
                     Lookup lookup,
-                    Path cwd,
-                    Path mavenHome,
-                    Path userHome,
-                    InputStream stdIn,
-                    OutputStream stdOut,
-                    OutputStream stdErr,
+                    @Nullable Path cwd,
+                    @Nullable Path mavenHome,
+                    @Nullable Path userHome,
+                    @Nullable InputStream stdIn,
+                    @Nullable OutputStream stdOut,
+                    @Nullable OutputStream stdErr,
                     boolean embedded) {
                 this.command = requireNonNull(command, "command");
                 this.commandName = requireNonNull(commandName, "commandName");
@@ -428,31 +454,37 @@ public Lookup lookup() {
                 return lookup;
             }
 
+            @Nullable
             @Override
             public Path cwd() {
                 return cwd;
             }
 
+            @Nullable
             @Override
             public Path mavenHome() {
                 return mavenHome;
             }
 
+            @Nullable
             @Override
             public Path userHome() {
                 return userHome;
             }
 
+            @Nullable
             @Override
             public InputStream stdIn() {
                 return stdIn;
             }
 
+            @Nullable
             @Override
             public OutputStream stdOut() {
                 return stdOut;
             }
 
+            @Nullable
             @Override
             public OutputStream stdErr() {
                 return stdErr;

api/maven-api-cli/src/main/java/org/apache/maven/api/cli/logging/AccumulatingLogger.java

@@ -22,6 +22,7 @@
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.atomic.AtomicReference;
 
+import org.apache.maven.api.annotations.Nullable;
 import org.apache.maven.api.cli.Logger;
 
 import static java.util.Objects.requireNonNull;
@@ -34,10 +35,10 @@ public class AccumulatingLogger implements Logger {
     private final AtomicReference<List<Entry>> entries = new AtomicReference<>(new CopyOnWriteArrayList<>());
 
     @Override
-    public void log(Level level, String message, Throwable error) {
+    public void log(Level level, String message, @Nullable Throwable error) {
         requireNonNull(level, "level");
         requireNonNull(message, "message");
-        entries.get().add(new Entry(level, message, error));
+        requireNonNull(entries.get()).add(new Entry(level, message, error));
     }
 
     @Override

api/maven-api-core/src/main/java/org/apache/maven/api/DependencyScope.java

@@ -26,6 +26,7 @@
 import org.apache.maven.api.annotations.Experimental;
 import org.apache.maven.api.annotations.Immutable;
 import org.apache.maven.api.annotations.Nonnull;
+import org.apache.maven.api.annotations.Nullable;
 
 /**
  * Indicates when the dependency will be used.
@@ -106,6 +107,7 @@ public enum DependencyScope {
      *
      * @param id the identifier of the scope (case-sensitive)
      */
+    @Nullable
     public static DependencyScope forId(String id) {
         return IDS.get(id);
     }

api/maven-api-core/src/main/java/org/apache/maven/api/JavaPathType.java

@@ -30,6 +30,7 @@
 
 import org.apache.maven.api.annotations.Experimental;
 import org.apache.maven.api.annotations.Nonnull;
+import org.apache.maven.api.annotations.Nullable;
 
 /**
  * The option of a Java command-line tool where to place the paths to some dependencies.
@@ -170,13 +171,15 @@ public static Modular patchModule(@Nonnull String moduleName) {
      *
      * @see #location()
      */
+    @Nullable
     private final JavaFileManager.Location location;
 
     /**
      * The tools option for this path, or {@code null} if none.
      *
      * @see #option()
      */
+    @Nullable
     private final String option;
 
     /**
@@ -185,7 +188,7 @@ public static Modular patchModule(@Nonnull String moduleName) {
      * @param location the {@code javax.tool} enumeration value, or {@code null} if none.
      * @param option the Java tools option for this path, or {@code null} if none
      */
-    JavaPathType(JavaFileManager.Location location, String option) {
+    JavaPathType(@Nullable JavaFileManager.Location location, @Nullable String option) {
         this.location = location;
         this.option = option;
     }
@@ -260,7 +263,7 @@ public String[] option(Iterable<? extends Path> paths) {
     /**
      * Implementation shared with {@link Modular}.
      */
-    final String[] format(String moduleName, Iterable<? extends Path> paths) {
+    final String[] format(@Nullable String moduleName, Iterable<? extends Path> paths) {
         if (option == null) {
             throw new IllegalStateException("No option is associated to this path type.");
         }

api/maven-api-core/src/main/java/org/apache/maven/api/ProtoSession.java

@@ -116,20 +116,29 @@ static Builder newBuilder() {
     }
 
     class Builder {
+        @Nullable
         private Map<String, String> userProperties;
+
+        @Nullable
         private Map<String, String> systemProperties;
+
+        @Nullable
         private Instant startTime;
+
+        @Nullable
         private Path topDirectory;
+
+        @Nullable
         private Path rootDirectory;
 
         private Builder() {}
 
         private Builder(
-                Map<String, String> userProperties,
-                Map<String, String> systemProperties,
-                Instant startTime,
-                Path topDirectory,
-                Path rootDirectory) {
+                @Nullable Map<String, String> userProperties,
+                @Nullable Map<String, String> systemProperties,
+                @Nullable Instant startTime,
+                @Nullable Path topDirectory,
+                @Nullable Path rootDirectory) {
             this.userProperties = userProperties;
             this.systemProperties = systemProperties;
             this.startTime = startTime;
@@ -163,7 +172,12 @@ public Builder withRootDirectory(@Nullable Path rootDirectory) {
         }
 
         public ProtoSession build() {
-            return new Impl(userProperties, systemProperties, startTime, topDirectory, rootDirectory);
+            return new Impl(
+                    requireNonNull(userProperties, "userProperties cannot be null"),
+                    requireNonNull(systemProperties, "systemProperties cannot be null"),
+                    requireNonNull(startTime, "startTime cannot be null"),
+                    requireNonNull(topDirectory, "topDirectory cannot be null"),
+                    rootDirectory);
         }
 
         private static class Impl implements ProtoSession {
@@ -172,14 +186,16 @@ private static class Impl implements ProtoSession {
             private final Map<String, String> effectiveProperties;
             private final Instant startTime;
             private final Path topDirectory;
+
+            @Nullable
             private final Path rootDirectory;
 
             private Impl(
-                    Map<String, String> userProperties,
-                    Map<String, String> systemProperties,
-                    Instant startTime,
-                    Path topDirectory,
-                    Path rootDirectory) {
+                    @Nonnull Map<String, String> userProperties,
+                    @Nonnull Map<String, String> systemProperties,
+                    @Nonnull Instant startTime,
+                    @Nonnull Path topDirectory,
+                    @Nullable Path rootDirectory) {
                 this.userProperties = Map.copyOf(userProperties);
                 this.systemProperties = Map.copyOf(systemProperties);
                 Map<String, String> cp = new HashMap<>(systemProperties);

api/maven-api-core/src/main/java/org/apache/maven/api/Session.java

@@ -263,7 +263,11 @@ default Map<String, String> getEffectiveProperties() {
      * @see ArtifactCoordinatesFactory#create(Session, String, String, String, String)
      */
     @Nonnull
-    ArtifactCoordinates createArtifactCoordinates(String groupId, String artifactId, String version, String extension);
+    ArtifactCoordinates createArtifactCoordinates(
+            @Nullable String groupId,
+            @Nullable String artifactId,
+            @Nullable String version,
+            @Nullable String extension);
 
     /**
      * Shortcut for {@code getService(ArtifactFactory.class).create(...)}.
@@ -280,7 +284,12 @@ default Map<String, String> getEffectiveProperties() {
      */
     @Nonnull
     ArtifactCoordinates createArtifactCoordinates(
-            String groupId, String artifactId, String version, String classifier, String extension, String type);
+            @Nullable String groupId,
+            @Nullable String artifactId,
+            @Nullable String version,
+            @Nullable String classifier,
+            @Nullable String extension,
+            @Nullable String type);
 
     /**
      * Shortcut for {@code getService(ArtifactFactory.class).create(...)}.
@@ -327,7 +336,11 @@ ArtifactCoordinates createArtifactCoordinates(
      * @see org.apache.maven.api.services.ArtifactFactory#create(Session, String, String, String, String)
      */
     @Nonnull
-    Artifact createArtifact(String groupId, String artifactId, String version, String extension);
+    Artifact createArtifact(
+            @Nullable String groupId,
+            @Nullable String artifactId,
+            @Nullable String version,
+            @Nullable String extension);
 
     /**
      * Shortcut for {@code getService(ArtifactFactory.class).create(...)}.
@@ -344,7 +357,12 @@ ArtifactCoordinates createArtifactCoordinates(
      */
     @Nonnull
     Artifact createArtifact(
-            String groupId, String artifactId, String version, String classifier, String extension, String type);
+            @Nullable String groupId,
+            @Nullable String artifactId,
+            @Nullable String version,
+            @Nullable String classifier,
+            @Nullable String extension,
+            @Nullable String type);
 
     /**
      * Shortcut for {@code getService(ArtifactFactory.class).createProduced(...)}.
@@ -358,7 +376,11 @@ Artifact createArtifact(
      * @see org.apache.maven.api.services.ArtifactFactory#createProduced(Session, String, String, String, String)
      */
     @Nonnull
-    ProducedArtifact createProducedArtifact(String groupId, String artifactId, String version, String extension);
+    ProducedArtifact createProducedArtifact(
+            @Nullable String groupId,
+            @Nullable String artifactId,
+            @Nullable String version,
+            @Nullable String extension);
 
     /**
      * Shortcut for {@code getService(ArtifactFactory.class).createProduced(...)}.
@@ -375,7 +397,12 @@ Artifact createArtifact(
      */
     @Nonnull
     ProducedArtifact createProducedArtifact(
-            String groupId, String artifactId, String version, String classifier, String extension, String type);
+            @Nullable String groupId,
+            @Nullable String artifactId,
+            @Nullable String version,
+            @Nullable String classifier,
+            @Nullable String extension,
+            @Nullable String type);
 
     /**
      * Shortcut for {@code getService(ArtifactResolver.class).resolve(...)}.

api/maven-api-core/src/main/java/org/apache/maven/api/feature/Features.java

@@ -61,11 +61,11 @@ public static boolean deployBuildPom(@Nullable Map<String, ?> userProperties) {
         return doGet(userProperties, Constants.MAVEN_DEPLOY_BUILD_POM, true);
     }
 
-    private static boolean doGet(Map<String, ?> userProperties, String key, boolean def) {
+    private static boolean doGet(@Nullable Map<String, ?> userProperties, String key, boolean def) {
         return doGet(userProperties != null ? userProperties.get(key) : null, def);
     }
 
-    private static boolean doGet(Object val, boolean def) {
+    private static boolean doGet(@Nullable Object val, boolean def) {
         if (val instanceof Boolean bool) {
             return bool;
         } else if (val != null) {