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Fix flaky TmpDir cleanup tests by removing race condition #101

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Merged
ericmj merged 1 commit into from
Mar 19, 2026
Merged

Fix flaky TmpDir cleanup tests by removing race condition #101

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8 changes: 4 additions & 4 deletions lib/preview/tmp_dir.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ defmodule Preview.TmpDir do
defp track(path) do
pid = self()
:ets.insert(@table, {pid, path})
GenServer.cast(__MODULE__, {:monitor, pid})
GenServer.call(__MODULE__, {:monitor, pid})
end

@impl true
Expand All @@ -46,12 +46,12 @@ defmodule Preview.TmpDir do
end

@impl true
def handle_cast({:monitor, pid}, state) do
def handle_call({:monitor, pid}, _from, state) do
if pid in state.monitors do
{:noreply, state}
{:reply, :ok, state}
else
Process.monitor(pid)
{:noreply, %{state | monitors: MapSet.put(state.monitors, pid)}}
{:reply, :ok, %{state | monitors: MapSet.put(state.monitors, pid)}}
end
end

Expand Down
55 changes: 32 additions & 23 deletions test/preview/tmp_dir_test.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,14 +15,15 @@ defmodule Preview.TmpDirTest do
test "cleanup on normal process exit" do
test_pid = self()

Task.start(fn ->
file = Preview.TmpDir.tmp_file("test")
dir = Preview.TmpDir.tmp_dir("test")
send(test_pid, {:paths, file, dir})
end)
{:ok, pid} =
Task.start(fn ->
file = Preview.TmpDir.tmp_file("test")
dir = Preview.TmpDir.tmp_dir("test")
send(test_pid, {:paths, file, dir})
end)

assert_receive {:paths, file, dir}
Process.sleep(100)
await_cleanup(pid)

refute File.exists?(file)
refute File.exists?(dir)
Expand All @@ -32,15 +33,16 @@ defmodule Preview.TmpDirTest do
test "cleanup on process crash" do
test_pid = self()

Task.start(fn ->
file = Preview.TmpDir.tmp_file("test")
dir = Preview.TmpDir.tmp_dir("test")
send(test_pid, {:paths, file, dir})
raise "crash"
end)
{:ok, pid} =
Task.start(fn ->
file = Preview.TmpDir.tmp_file("test")
dir = Preview.TmpDir.tmp_dir("test")
send(test_pid, {:paths, file, dir})
raise "crash"
end)

assert_receive {:paths, file, dir}
Process.sleep(100)
await_cleanup(pid)

refute File.exists?(file)
refute File.exists?(dir)
Expand All @@ -49,26 +51,33 @@ defmodule Preview.TmpDirTest do
test "multiple paths for one process" do
test_pid = self()

Task.start(fn ->
paths =
for i <- 1..5 do
file = Preview.TmpDir.tmp_file("test-#{i}")
dir = Preview.TmpDir.tmp_dir("test-#{i}")
{file, dir}
end
{:ok, pid} =
Task.start(fn ->
paths =
for i <- 1..5 do
file = Preview.TmpDir.tmp_file("test-#{i}")
dir = Preview.TmpDir.tmp_dir("test-#{i}")
{file, dir}
end

send(test_pid, {:paths, paths})
end)
send(test_pid, {:paths, paths})
end)

assert_receive {:paths, paths}
Process.sleep(100)
await_cleanup(pid)

for {file, dir} <- paths do
refute File.exists?(file)
refute File.exists?(dir)
end
end

defp await_cleanup(pid) do
ref = Process.monitor(pid)
assert_receive {:DOWN, ^ref, _, _, _}, 5000
:sys.get_state(Preview.TmpDir)
end

test "paths persist while process is alive" do
file = Preview.TmpDir.tmp_file("test")
dir = Preview.TmpDir.tmp_dir("test")
Expand Down
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