home-assistant: reduce component tests processes

Component tests are often of lesser quality, which may lead to spurious
errors when run with high parallelization. Reducing to 4 processes
aligns the setup with what GitHub actions provides, which is what
upstream uses to test.

pkgs/servers/home-assistant/default.nix

@@ -293,8 +293,6 @@ in python.pkgs.buildPythonApplication rec {
   ];
 
   pytestFlagsArray = [
-    # parallelize test run
-    "--numprocesses $NIX_BUILD_CORES"
     # assign tests grouped by file to workers
     "--dist loadfile"
     # retry racy tests that end in "RuntimeError: Event loop is closed"

pkgs/servers/home-assistant/tests.nix

@@ -56,7 +56,11 @@ in lib.listToAttrs (map (component: lib.nameValuePair component (
     disabledTests = old.disabledTests ++ extraDisabledTests.${component} or [];
     disabledTestPaths = old.disabledTestPaths ++ extraDisabledTestPaths.${component} or [ ];
 
+    # components are more often racy than the core
+    dontUsePytestXdist = true;
+
     pytestFlagsArray = lib.remove "tests" old.pytestFlagsArray
+      ++ [ "--numprocesses=4" ]
       ++ extraPytestFlagsArray.${component} or [ ]
       ++ [ "tests/components/${component}" ];