From dc1a193d79b2b694a98af72d63beff6ec35de17b Mon Sep 17 00:00:00 2001
From: Greger Stolt Nilsen <gregersn@gmail.com>
Date: Wed, 6 Sep 2023 18:03:25 +0200
Subject: [PATCH] Do not use code location for Gitlab fingerprints.

Using code location when creating hash for Gitlab fingerprints
makes the codequality reports in Gitlab very unstable.
Any change of position would trigger both a "fixed" message, and
a "new problem detected" message in Gitlab, making it very noisy.
---
 crates/ruff/src/message/gitlab.rs | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/crates/ruff/src/message/gitlab.rs b/crates/ruff/src/message/gitlab.rs
index e799823fda827e..355472212de1f6 100644
--- a/crates/ruff/src/message/gitlab.rs
+++ b/crates/ruff/src/message/gitlab.rs
@@ -1,4 +1,5 @@
 use std::collections::hash_map::DefaultHasher;
+use std::collections::HashSet;
 use std::hash::{Hash, Hasher};
 use std::io::Write;
 
@@ -6,8 +7,6 @@ use serde::ser::SerializeSeq;
 use serde::{Serialize, Serializer};
 use serde_json::json;
 
-use ruff_source_file::SourceLocation;
-
 use crate::fs::{relativize_path, relativize_path_to};
 use crate::message::{Emitter, EmitterContext, Message};
 use crate::registry::AsRule;
@@ -58,6 +57,7 @@ impl Serialize for SerializedMessages<'_> {
         S: Serializer,
     {
         let mut s = serializer.serialize_seq(Some(self.messages.len()))?;
+        let mut fingerprints = HashSet::<u64>::with_capacity(self.messages.len());
 
         for message in self.messages {
             let start_location = message.compute_start_location();
@@ -82,10 +82,19 @@ impl Serialize for SerializedMessages<'_> {
                 |project_dir| relativize_path_to(message.filename(), project_dir),
             );
 
+            let mut message_fingerprint = fingerprint(message, 0);
+
+            // Make sure that we do not get a fingerprint that is already in use
+            // by adding in the previously generated one.
+            while fingerprints.contains(&message_fingerprint) {
+                message_fingerprint = fingerprint(message, message_fingerprint);
+            }
+            fingerprints.insert(message_fingerprint);
+
             let value = json!({
                 "description": format!("({}) {}", message.kind.rule().noqa_code(), message.kind.body),
                 "severity": "major",
-                "fingerprint": fingerprint(message, &start_location, &end_location),
+                "fingerprint": format!("{:x}", message_fingerprint),
                 "location": {
                     "path": path,
                     "lines": lines
@@ -100,11 +109,7 @@ impl Serialize for SerializedMessages<'_> {
 }
 
 /// Generate a unique fingerprint to identify a violation.
-fn fingerprint(
-    message: &Message,
-    start_location: &SourceLocation,
-    end_location: &SourceLocation,
-) -> String {
+fn fingerprint(message: &Message, salt: u64) -> u64 {
     let Message {
         kind,
         range: _,
@@ -115,12 +120,11 @@ fn fingerprint(
 
     let mut hasher = DefaultHasher::new();
 
-    kind.rule().hash(&mut hasher);
-    start_location.hash(&mut hasher);
-    end_location.hash(&mut hasher);
+    salt.hash(&mut hasher);
+    kind.name.hash(&mut hasher);
     file.name().hash(&mut hasher);
 
-    format!("{:x}", hasher.finish())
+    hasher.finish()
 }
 
 #[cfg(test)]