From 7b92403abf2acb316084df983f51ebed8fd12cef Mon Sep 17 00:00:00 2001
From: Kun Ren <renkun@outlook.com>
Date: Sat, 1 Aug 2026 21:46:32 +0800
Subject: [PATCH] Fix diagnostics cancellation interrupt race

---
 NEWS.md                    |  2 ++
 R/task.R                   |  8 +++++---
 tests/testthat/test-task.R | 26 ++++++++++++++++++++++++++
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index e9797827..bd938176 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # languageserver 0.3.18
 
+- Retire persistent `callr` workers when cancelling tasks so a late interrupt
+  cannot leak into the next diagnostics run.
 - Add preferred quick fixes for common `lintr` diagnostics and a conflict-aware
   `source.fixAll` action, while making multi-line `nolint` actions apply to every
   affected line.
diff --git a/R/task.R b/R/task.R
index ed4bdbbe..66503b39 100644
--- a/R/task.R
+++ b/R/task.R
@@ -90,9 +90,11 @@ Task <- R6::R6Class("Task",
             private$cancelled <- TRUE
             if (!is.null(private$session)) {
                 if (!identical(Sys.getenv("R_COVR"), "true")) {
-                    # Do not close the session, it is persistent and managed by TaskManager.
-                    # Just try to interrupt the ongoing computation.
-                    private$session$interrupt()
+                    # An interrupt can arrive after this call has completed and
+                    # interrupt the next task on the persistent session. Retire
+                    # the worker instead so cancellation cannot leak across tasks.
+                    private$session$kill(
+                        grace = 0, close_connections = FALSE)
                 }
             } else if (!is.null(private$process) && private$process$is_alive()) {
                 if (identical(Sys.getenv("R_COVR"), "true")) {
diff --git a/tests/testthat/test-task.R b/tests/testthat/test-task.R
index 83132291..5eef45f0 100644
--- a/tests/testthat/test-task.R
+++ b/tests/testthat/test-task.R
@@ -158,6 +158,32 @@ test_that("TaskManager refreshes pending task recency", {
     tm$stop()
 })
 
+test_that("Task cancellation retires its persistent session", {
+    withr::local_envvar(R_COVR = "false")
+    state <- "idle"
+    killed <- FALSE
+    interrupted <- FALSE
+    session <- list(
+        call = function(...) state <<- "busy",
+        get_state = function() state,
+        read = function() NULL,
+        kill = function(grace, close_connections) {
+            expect_equal(grace, 0)
+            expect_false(close_connections)
+            killed <<- TRUE
+            state <<- "finished"
+        },
+        interrupt = function() interrupted <<- TRUE
+    )
+    task <- create_task(function() NULL, list())
+
+    task$start(session)
+    task$kill()
+
+    expect_true(killed)
+    expect_false(interrupted)
+})
+
 test_that("TaskManager does not overprovision while a session starts", {
     tm <- TaskManager$new(
         "starting", use_session = TRUE, min_idle_sessions = 0,