From 8d9f50c68af853b227a13f182589805292a1c9aa Mon Sep 17 00:00:00 2001
From: Chris Povirk <cpovirk@google.com>
Date: Thu, 13 Jan 2022 20:36:54 -0500
Subject: [PATCH] Recognize an experimental protobuf @PolyNull annotation
 (#147)

Co-authored-by: Werner Dietl <wdietl@gmail.com>
---
 .../NullnessAnnotatedTypeFactory.java         | 12 +++++++++
 docs/manual/nullness-checker.tex              | 26 +++++++++++++++++--
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/checker/src/main/java/org/checkerframework/checker/nullness/NullnessAnnotatedTypeFactory.java b/checker/src/main/java/org/checkerframework/checker/nullness/NullnessAnnotatedTypeFactory.java
index cbcaeb94480..947b1595e49 100644
--- a/checker/src/main/java/org/checkerframework/checker/nullness/NullnessAnnotatedTypeFactory.java
+++ b/checker/src/main/java/org/checkerframework/checker/nullness/NullnessAnnotatedTypeFactory.java
@@ -299,6 +299,17 @@ public class NullnessAnnotatedTypeFactory
                     // https://github.com/reactor/reactor-core/blob/main/reactor-core/src/main/java/reactor/util/annotation/Nullable.java
                     "reactor.util.annotation.Nullable");
 
+    // List is in alphabetical order.  If you update it, also update
+    // ../../../../../../../../docs/manual/nullness-checker.tex .
+    // See more comments with NONNULL_ALIASES above.
+    /** Aliases for {@code @PolyNull}. */
+    @SuppressWarnings(
+            "signature:assignment.type.incompatible") // Class names intentionally obfuscated
+    private static final List<@FullyQualifiedName String> POLYNULL_ALIASES =
+            Arrays.asList(
+                    // "com.google.protobuf.Internal.ProtoPassThroughNullness",
+                    "com.go".toString() + "ogle.protobuf.Internal.ProtoPassThroughNullness");
+
     /**
      * Creates a NullnessAnnotatedTypeFactory.
      *
@@ -316,6 +327,7 @@ public NullnessAnnotatedTypeFactory(BaseTypeChecker checker) {
 
         NONNULL_ALIASES.forEach(annotation -> addAliasedTypeAnnotation(annotation, NONNULL));
         NULLABLE_ALIASES.forEach(annotation -> addAliasedTypeAnnotation(annotation, NULLABLE));
+        POLYNULL_ALIASES.forEach(annotation -> addAliasedTypeAnnotation(annotation, POLYNULL));
 
         // Add compatibility annotations:
         addAliasedTypeAnnotation(
diff --git a/docs/manual/nullness-checker.tex b/docs/manual/nullness-checker.tex
index 3454b1f405b..12ac7033a8f 100644
--- a/docs/manual/nullness-checker.tex
+++ b/docs/manual/nullness-checker.tex
@@ -915,8 +915,9 @@
 annotation, the Checker Framework can type-check your code.
 It treats annotations from other tools
 as if you had written the corresponding annotation from the
-Nullness Checker, as described in Figures~\ref{fig-nullness-refactoring-nonnull}
-and \ref{fig-nullness-refactoring-nullable}.
+Nullness Checker, as described in Figures~\ref{fig-nullness-refactoring-nonnull},
+\ref{fig-nullness-refactoring-nullable}, and
+\ref{fig-nullness-refactoring-polynull}.
 If the other annotation is a declaration annotation, it may be moved; see
 Section~\ref{declaration-annotations-moved}.
 
@@ -1046,6 +1047,27 @@
 \label{fig-nullness-refactoring-nullable}
 \end{figure}
 
+% See comments above previous table.
+\begin{figure}
+\begin{center}
+\begin{tabular}{ll}
+\begin{tabular}{|l|l|}
+\hline
+ ~com.google.protobuf.Internal.ProtoPassThroughNullness~ \\ \hline
+\end{tabular}
+&
+$\Rightarrow$
+~org.checkerframework.checker.nullness.qual.PolyNull~
+\end{tabular}
+\end{center}
+%BEGIN LATEX
+\vspace{-1.5\baselineskip}
+%END LATEX
+\caption{Correspondence between other nullness annotations and the
+  Checker Framework's \<PolyNull> annotation.}
+\label{fig-nullness-refactoring-polynull}
+\end{figure}
+
 %% Removed, because it's tedious and should be obvious to a decent programmer.
 % Your IDE may be able to do that for you.  Alternately, do the following:
 % \begin{enumerate}