fix: solve false positive ChannelPriorityCombinationError (#4943)

Co-authored-by: Ruben Arts <[email protected]>

Author: MartinJepsen

crates/pixi_core/src/workspace/environment.rs

@@ -1026,4 +1026,95 @@ mod tests {
             pixi_manifest::SolveStrategy::Highest
         );
     }
+
+    /// Test that combining channel priorities from multiple features
+    /// results in a ChannelPriorityCombinationError if the priorities conflict.
+    #[test]
+    fn test_channel_priority_compatibility() {
+        use crate::workspace::grouped_environment::GroupedEnvironment;
+
+        // First part - priorities are compatible
+        {
+            let contents = r#"
+            [project]
+            name = "test"
+            platforms = ["linux-64"]
+            channels = ["conda-forge"]
+            channel-priority = "disabled"
+
+            [feature.feat1]
+            channel-priority = "disabled"  # Is ok as it's the same as the default
+
+            [environments]
+            test = ["feat1"]
+            "#;
+
+            let workspace = Workspace::from_str(Path::new("pixi.toml"), contents).unwrap();
+            let env = workspace.environment("test").unwrap();
+            let grouped_env = GroupedEnvironment::from(env);
+
+            // This should not return an error because both features have the same channel-priority
+            let result = grouped_env.channel_priority();
+            assert!(
+                result.is_ok(),
+                "Channel priorities were expected to be compatible"
+            );
+        }
+        // Second part, priorities conflict
+        {
+            let contents = r#"
+            [project]
+            name = "test"
+            platforms = ["linux-64"]
+            channels = ["conda-forge"]
+            channel-priority = "disabled"
+
+            [feature.feat1]
+            channel-priority = "strict"  # Conflicts with the default
+
+            [environments]
+            test = ["feat1"]
+            "#;
+
+            let workspace = Workspace::from_str(Path::new("pixi.toml"), contents).unwrap();
+            let env = workspace.environment("test").unwrap();
+            let grouped_env = GroupedEnvironment::from(env);
+
+            // This should return an error because the features have conflicting channel-priorities
+            let result = grouped_env.channel_priority();
+            assert!(
+                result.is_err(),
+                "Channel priorities were expected to be incompatible"
+            );
+        }
+        // Third part, there is a default priority, but the feature doesn't have a priority set.
+        {
+            let contents = r#"
+            [project]
+            name = "test"
+            platforms = ["linux-64"]
+            channels = ["conda-forge"]
+            channel-priority = "disabled"
+
+            # Adding a dependency, just so the feature has at least some data
+            [feature.feat1.dependencies]
+            python = ">=3.13"
+
+            [environments]
+            test = ["feat1"]
+            "#;
+
+            let workspace = Workspace::from_str(Path::new("pixi.toml"), contents).unwrap();
+            let env = workspace.environment("test").unwrap();
+            let grouped_env = GroupedEnvironment::from(env);
+
+            // This should not return an error because the default feature sets the priority
+            let result = grouped_env.channel_priority();
+            assert_eq!(
+                result.unwrap(),
+                Some(pixi_manifest::ChannelPriority::Disabled),
+                "Channel priorities were expected to be compatible"
+            );
+        }
+    }
 }

crates/pixi_manifest/src/features_ext.rs

@@ -68,7 +68,7 @@ pub trait FeaturesExt<'source>: HasWorkspaceManifest<'source> + HasFeaturesIter<
             .collect()
     }
 
-    /// Returns the channel priority, error on multiple values, return None if
+    /// Returns the channel priority, error on multiple, different values, return None if
     /// no value is set.
     ///
     /// When using multiple channel priorities over different features we should
@@ -77,7 +77,8 @@ pub trait FeaturesExt<'source>: HasWorkspaceManifest<'source> + HasFeaturesIter<
         let mut channel_priority = None;
         for feature in self.features() {
             if let Some(priority) = feature.channel_priority {
-                if channel_priority == Some(priority) {
+                // If we already have a priority and it's different, error
+                if channel_priority.is_some() && channel_priority != Some(priority) {
                     return Err(ChannelPriorityCombinationError);
                 }
                 channel_priority = Some(priority);