From cb2e17d383cfe9498f54c0b57b2ee06885ff436c Mon Sep 17 00:00:00 2001
From: Philipp Zeipert <philipp.zeipert@teampicnic.com>
Date: Tue, 17 Dec 2024 11:35:21 +0100
Subject: [PATCH] Introduce `StreamMapToValuesFromMap` Refaster rule

---
 .../picnic/errorprone/refasterrules/StreamRules.java | 12 ++++++++++++
 .../refasterrules/StreamRulesTestInput.java          |  5 +++++
 .../refasterrules/StreamRulesTestOutput.java         |  5 +++++
 3 files changed, 22 insertions(+)

diff --git a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/StreamRules.java b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/StreamRules.java
index e7bea741423..adfa70d5044 100644
--- a/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/StreamRules.java
+++ b/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/StreamRules.java
@@ -297,6 +297,18 @@ boolean after(Stream<T> stream) {
     }
   }
 
+  static final class StreamMapToValuesFromMap<K, V> {
+    @BeforeTemplate
+    Stream<V> before(Stream<K> stream, Map<K, V> map) {
+      return stream.filter(map::containsKey).map(map::get);
+    }
+
+    @AfterTemplate
+    Stream<V> after(Stream<K> stream, Map<K, V> map) {
+      return stream.map(map::get).filter(Objects::nonNull);
+    }
+  }
+
   static final class StreamMin<T> {
     @BeforeTemplate
     @SuppressWarnings("java:S4266" /* This violation will be rewritten. */)
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestInput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestInput.java
index 5126726c3bf..3790e028bde 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestInput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestInput.java
@@ -141,6 +141,11 @@ boolean testStreamFindAnyIsPresent() {
     return Stream.of(1).findFirst().isPresent();
   }
 
+  Stream<String> testStreamMapToValuesFromMap() {
+    ImmutableMap<String, String> map = ImmutableMap.of("foo", "bar");
+    return Stream.of("foo").filter(map::containsKey).map(map::get);
+  }
+
   ImmutableSet<Optional<String>> testStreamMin() {
     return ImmutableSet.of(
         Stream.of("foo").max(comparingInt(String::length).reversed()),
diff --git a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestOutput.java b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestOutput.java
index a11b7ca644c..10b0050c54f 100644
--- a/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestOutput.java
+++ b/error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/StreamRulesTestOutput.java
@@ -141,6 +141,11 @@ boolean testStreamFindAnyIsPresent() {
     return Stream.of(1).findAny().isPresent();
   }
 
+  Stream<String> testStreamMapToValuesFromMap() {
+    ImmutableMap<String, String> map = ImmutableMap.of("foo", "bar");
+    return Stream.of("foo").map(map::get).filter(Objects::nonNull);
+  }
+
   ImmutableSet<Optional<String>> testStreamMin() {
     return ImmutableSet.of(
         Stream.of("foo").min(comparingInt(String::length)),