[fixes #1812] `@Singular` marked collections which nevertheless somehow ended up null would cause an NPE during `toBuilder()` invocations.

5 files changed, 132 insertions, 2 deletions

diff --git a/test/transform/resource/after-delombok/BuilderSingularToBuilderWithNull.java b/test/transform/resource/after-delombok/BuilderSingularToBuilderWithNull.java
new file mode 100644
index 00000000..1f472438
--- /dev/null
+++ b/test/transform/resource/after-delombok/BuilderSingularToBuilderWithNull.java
@@ -0,0 +1,63 @@
+class BuilderSingularToBuilderWithNull {
+	private java.util.List<String> elems;
+	public static void test() {
+		new BuilderSingularToBuilderWithNull(null).toBuilder();
+	}
+	@java.lang.SuppressWarnings("all")
+	BuilderSingularToBuilderWithNull(final java.util.List<String> elems) {
+		this.elems = elems;
+	}
+	@java.lang.SuppressWarnings("all")
+	public static class BuilderSingularToBuilderWithNullBuilder {
+		@java.lang.SuppressWarnings("all")
+		private java.util.ArrayList<String> elems;
+		@java.lang.SuppressWarnings("all")
+		BuilderSingularToBuilderWithNullBuilder() {
+		}
+		@java.lang.SuppressWarnings("all")
+		public BuilderSingularToBuilderWithNullBuilder elem(final String elem) {
+			if (this.elems == null) this.elems = new java.util.ArrayList<String>();
+			this.elems.add(elem);
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public BuilderSingularToBuilderWithNullBuilder elems(final java.util.Collection<? extends String> elems) {
+			if (this.elems == null) this.elems = new java.util.ArrayList<String>();
+			this.elems.addAll(elems);
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public BuilderSingularToBuilderWithNullBuilder clearElems() {
+			if (this.elems != null) this.elems.clear();
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public BuilderSingularToBuilderWithNull build() {
+			java.util.List<String> elems;
+			switch (this.elems == null ? 0 : this.elems.size()) {
+			case 0: 
+				elems = java.util.Collections.emptyList();
+				break;
+			case 1: 
+				elems = java.util.Collections.singletonList(this.elems.get(0));
+				break;
+			default: 
+				elems = java.util.Collections.unmodifiableList(new java.util.ArrayList<String>(this.elems));
+			}
+			return new BuilderSingularToBuilderWithNull(elems);
+		}
+		@java.lang.Override
+		@java.lang.SuppressWarnings("all")
+		public java.lang.String toString() {
+			return "BuilderSingularToBuilderWithNull.BuilderSingularToBuilderWithNullBuilder(elems=" + this.elems + ")";
+		}
+	}
+	@java.lang.SuppressWarnings("all")
+	public static BuilderSingularToBuilderWithNullBuilder builder() {
+		return new BuilderSingularToBuilderWithNullBuilder();
+	}
+	@java.lang.SuppressWarnings("all")
+	public BuilderSingularToBuilderWithNullBuilder toBuilder() {
+		return new BuilderSingularToBuilderWithNullBuilder().elems(this.elems == null ? java.util.Collections.emptyList() : this.elems);
+	}
+}
diff --git a/test/transform/resource/after-delombok/BuilderWithToBuilder.java b/test/transform/resource/after-delombok/BuilderWithToBuilder.java
index 46387f0f..b644a16f 100644
--- a/test/transform/resource/after-delombok/BuilderWithToBuilder.java
+++ b/test/transform/resource/after-delombok/BuilderWithToBuilder.java
@@ -86,7 +86,7 @@ class BuilderWithToBuilder<T> {
 	}
 	@java.lang.SuppressWarnings("all")
 	public BuilderWithToBuilderBuilder<T> toBuilder() {
-		return new BuilderWithToBuilderBuilder<T>().one(this.mOne).two(this.mTwo).foo(BuilderWithToBuilder.rrr(this)).bars(this.bars);
+		return new BuilderWithToBuilderBuilder<T>().one(this.mOne).two(this.mTwo).foo(BuilderWithToBuilder.rrr(this)).bars(this.bars == null ? java.util.Collections.emptyList() : this.bars);
 	}
 }
 class ConstructorWithToBuilder<T> {
diff --git a/test/transform/resource/after-ecj/BuilderSingularToBuilderWithNull.java b/test/transform/resource/after-ecj/BuilderSingularToBuilderWithNull.java
new file mode 100644
index 00000000..7265e17a
--- /dev/null
+++ b/test/transform/resource/after-ecj/BuilderSingularToBuilderWithNull.java
@@ -0,0 +1,57 @@
+import lombok.Singular;
+@lombok.Builder(toBuilder = true) class BuilderSingularToBuilderWithNull {
+  public static @java.lang.SuppressWarnings("all") class BuilderSingularToBuilderWithNullBuilder {
+    private @java.lang.SuppressWarnings("all") java.util.ArrayList<String> elems;
+    @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNullBuilder() {
+      super();
+    }
+    public @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNullBuilder elem(String elem) {
+      if ((this.elems == null))
+          this.elems = new java.util.ArrayList<String>();
+      this.elems.add(elem);
+      return this;
+    }
+    public @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNullBuilder elems(java.util.Collection<? extends String> elems) {
+      if ((this.elems == null))
+          this.elems = new java.util.ArrayList<String>();
+      this.elems.addAll(elems);
+      return this;
+    }
+    public @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNullBuilder clearElems() {
+      if ((this.elems != null))
+          this.elems.clear();
+      return this;
+    }
+    public @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNull build() {
+      java.util.List<String> elems;
+      switch (((this.elems == null) ? 0 : this.elems.size())) {
+      case 0 :
+          elems = java.util.Collections.emptyList();
+          break;
+      case 1 :
+          elems = java.util.Collections.singletonList(this.elems.get(0));
+          break;
+      default :
+          elems = java.util.Collections.unmodifiableList(new java.util.ArrayList<String>(this.elems));
+      }
+      return new BuilderSingularToBuilderWithNull(elems);
+    }
+    public @java.lang.Override @java.lang.SuppressWarnings("all") java.lang.String toString() {
+      return (("BuilderSingularToBuilderWithNull.BuilderSingularToBuilderWithNullBuilder(elems=" + this.elems) + ")");
+    }
+  }
+  private @Singular java.util.List<String> elems;
+  public static void test() {
+    new BuilderSingularToBuilderWithNull(null).toBuilder();
+  }
+  @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNull(final java.util.List<String> elems) {
+    super();
+    this.elems = elems;
+  }
+  public static @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNullBuilder builder() {
+    return new BuilderSingularToBuilderWithNullBuilder();
+  }
+  public @java.lang.SuppressWarnings("all") BuilderSingularToBuilderWithNullBuilder toBuilder() {
+    return new BuilderSingularToBuilderWithNullBuilder().elems(((this.elems == null) ? java.util.Collections.emptyList() : this.elems));
+  }
+}
diff --git a/test/transform/resource/after-ecj/BuilderWithToBuilder.java b/test/transform/resource/after-ecj/BuilderWithToBuilder.java
index d304293c..b9cc27dd 100644
--- a/test/transform/resource/after-ecj/BuilderWithToBuilder.java
+++ b/test/transform/resource/after-ecj/BuilderWithToBuilder.java
@@ -74,7 +74,7 @@ import lombok.Builder;
     return new BuilderWithToBuilderBuilder<T>();
   }
   public @java.lang.SuppressWarnings("all") BuilderWithToBuilderBuilder<T> toBuilder() {
-    return new BuilderWithToBuilderBuilder<T>().one(this.mOne).two(this.mTwo).foo(BuilderWithToBuilder.rrr(this)).bars(this.bars);
+    return new BuilderWithToBuilderBuilder<T>().one(this.mOne).two(this.mTwo).foo(BuilderWithToBuilder.rrr(this)).bars(((this.bars == null) ? java.util.Collections.emptyList() : this.bars));
   }
 }
 @lombok.experimental.Accessors(prefix = "m") class ConstructorWithToBuilder<T> {
diff --git a/test/transform/resource/before/BuilderSingularToBuilderWithNull.java b/test/transform/resource/before/BuilderSingularToBuilderWithNull.java
new file mode 100644
index 00000000..92a102cb
--- /dev/null
+++ b/test/transform/resource/before/BuilderSingularToBuilderWithNull.java
@@ -0,0 +1,10 @@
+import lombok.Singular;
+
+@lombok.Builder(toBuilder = true)
+class BuilderSingularToBuilderWithNull {
+	@Singular private java.util.List<String> elems;
+	
+	public static void test() {
+		new BuilderSingularToBuilderWithNull(null).toBuilder();
+	}
+}