test diagnostics changes upon config invalidation

Summary:
D87952758 will also fix this bug. if an existing error change, it previously would not update

I would've liked to do this as a before/after test, but I didn't think it was worth adding an expect_diagnostisc_message_does_not_contain (because that would pass too frequently and likely be useless)

Reviewed By: yangdanny97

Differential Revision: D88529135

fbshipit-source-id: 6788b614bb6567c66259b663719741131c3e7da5

Author: kinto0

pyrefly/lib/test/lsp/lsp_interaction/configuration.rs

@@ -357,6 +357,58 @@ fn test_interpreter_change_removes_type_errors() {
     interaction.shutdown().unwrap();
 }
 
+// Only run this test on unix since windows has no way to mock a .exe without compiling something
+// (we call python with python.exe)
+#[cfg(unix)]
+#[test]
+fn test_interpreter_change_changes_existing_type_errors() {
+    let test_files_root = get_test_files_root();
+    let interpreter_path = setup_dummy_interpreter(
+        &test_files_root
+            .path()
+            .join("interpreter_with_no_site_packages"),
+    );
+
+    let mut interaction = LspInteraction::new();
+    interaction.set_root(test_files_root.path().to_path_buf());
+    interaction
+        .initialize(InitializeSettings {
+            configuration: Some(Some(
+                json!([{"pyrefly": {"displayTypeErrors": "force-on"}}]),
+            )),
+            ..Default::default()
+        })
+        .unwrap();
+
+    interaction.client.did_open("custom_interpreter/src/foo.py");
+    // Without any interpreter configured, there should be 1 import error
+    interaction
+        .client
+        .expect_publish_diagnostics_error_count(
+            test_files_root.path().join("custom_interpreter/src/foo.py"),
+            1,
+        )
+        .unwrap();
+    interaction.client.did_change_configuration();
+    interaction
+        .client
+        .expect_request::<WorkspaceConfiguration>(json!({"items":[{"section":"python"}]}))
+        .unwrap()
+        .send_configuration_response(json!([
+            {
+                "pythonPath": interpreter_path.to_str().unwrap()
+            }
+        ]));
+    interaction
+        .client
+        .expect_publish_diagnostics_message_contains(
+            test_files_root.path().join("custom_interpreter/src/foo.py"),
+            "interpreter_with_no_site_packages",
+        )
+        .unwrap();
+    interaction.shutdown().unwrap();
+}
+
 #[test]
 fn test_disable_language_services() {
     let test_files_root = get_test_files_root();

pyrefly/lib/test/lsp/lsp_interaction/object_model.rs

@@ -824,6 +824,41 @@ impl TestClient {
         })
     }
 
+    /// Wait for a publishDiagnostics notification, then check if it contains the message
+    pub fn expect_publish_diagnostics_message_contains(
+        &self,
+        path: PathBuf,
+        message: &str,
+    ) -> Result<(), LspMessageError> {
+        self.expect_message(
+            &format!(
+                "publishDiagnostics notification containing message '{message}' for file: {}",
+                path.display()
+            ),
+            |msg| {
+                if let Message::Notification(x) = msg
+                    && x.method == PublishDiagnostics::METHOD
+                {
+                    let params: PublishDiagnosticsParams =
+                        serde_json::from_value(x.params).unwrap();
+                    if params.uri.to_file_path().ok().as_ref() == Some(&path)
+                        && params
+                            .diagnostics
+                            .iter()
+                            .any(|d| d.message.contains(message))
+                    {
+                        Some(())
+                    } else {
+                        None
+                    }
+                } else {
+                    None
+                }
+            },
+        )?;
+        Ok(())
+    }
+
     /// Wait for a publishDiagnostics notification, then check if it has the correct path and count
     pub fn expect_publish_diagnostics_error_count(
         &self,