populate: stop the ssh master also when a signal ends populate

The shell doesn't run the EXIT trap when a signal ends it, so an
interrupted deploy leaves the ssh master, for an hour, and populate's
temporary directory.  Populate traps HUP, INT, and TERM and exits, which
runs the EXIT trap.

The shell runs a trap once the command it waits for ends.  A signal to
the process group, like the one of an interrupt key, of a closed terminal,
or of timeout, ends that command as well.  A signal to populate alone
takes effect after the step that is running.

Phases of scenarios can end populate after some seconds.  An edge case
does so while a pipe source's command sleeps, and checks that neither the
ssh master nor the temporary directory remain.

1 files changed, 27 insertions, 3 deletions

diff --git a/tests/scenarios.nix b/tests/scenarios.nix
index 2fb6609..3113586 100644
--- a/tests/scenarios.nix
+++ b/tests/scenarios.nix
@@ -97,10 +97,11 @@ let
     # targetPath deploys to another path than the scenario's target
     # directory, and controlTargetPath is the control for a path that makes
     # evaluation fail.  env sets environment variables for populate, as
-    # arguments of env.
+    # arguments of env.  interrupt ends populate after that many seconds,
+    # which it's expected not to finish before.
     phase = {
       sources, backup ? false, prune ? false, deploy ? null,
-      targetPath ? path, env ? "",
+      targetPath ? path, env ? "", interrupt ? null,
       expect ? "success", control ? null, controlTargetPath ? null,
       check ? "", mutate ? null, checkDeployer ? null, mutateDeployer ? null,
     }: let
@@ -135,7 +136,7 @@ let
           null
       else {
         populate = toString (command sources targetPath);
-        inherit env;
+        inherit env interrupt;
         expect = if expect == "success" then null else expect.fail;
         # No phase gets around checking the canaries.
         check = script (check + "\ncanary_check\n");
@@ -1320,6 +1321,29 @@ assert !(krops.isLocalTarget (targets.remote "/"));
         }
       ];
     }))
+    # A signal ending populate leaves neither the ssh master nor the
+    # temporary directory.
+    (s "interrupt" {
+      prepareDeployer = ''
+        find "''${TMPDIR:-/tmp}" -maxdepth 1 -name 'populate.*' -exec rm -fR {} +
+      '';
+      phases = [{
+        sources.x.pipe = "/fixtures/pipe-slow";
+        interrupt = 3;
+        checkDeployer = ''
+          for i in 1 2 3 4 5 6 7 8 9 10; do
+            if ! pgrep -f 'ssh: .*/populate\..*\[mux\]' >/dev/null; then
+              break
+            fi
+            sleep 0.5
+          done
+          ! pgrep -f 'ssh: .*/populate\..*\[mux\]' >/dev/null ||
+            fail "ssh master remains"
+          expect_eq "temporary directories" \
+              "$(find "''${TMPDIR:-/tmp}" -maxdepth 1 -name 'populate.*')" ""
+        '';
+      }];
+    })
     # An input of an input drawn from a source that draws inputs itself
     # gets drawn from another source.
     (modes "override" ({ draw, flake, ... }: {