feat(serviceGroups): add hooks

docs/src/getting_started.md

@@ -188,6 +188,25 @@ This will add two commands to the devshell: `database:start` and
 group in the foreground and shows their output. `database:stop` can be executed
 in a different shell to stop the processes (or press Ctrl-C in the main shell).
 
+You can also run commands before and after starting/stopping a service group.
+For example, to run database migrations before starting and cleanup after stopping:
+```toml
+[serviceGroups.api]
+description = "API server and related services"
+beforeStart = """
+echo "Running database migrations..."
+./manage.py migrate
+"""
+afterStop = """
+echo "Cleaning up temp files..."
+rm -rf /tmp/api_*
+"""
+[serviceGroups.api.services.django]
+command = "python manage.py runserver 0.0.0.0:8000"
+[serviceGroups.api.services.redis]
+command = "redis-server"
+```
+
 ## Wrapping up
 
 **devshell** is extensible in many different ways. In the next chapters we will

docs/src/modules_schema.md

@@ -1284,6 +1284,86 @@ attribute set of (submodule)
 
 - [modules/services.nix](https://github.com/numtide/devshell/tree/main/modules/services.nix)
 
+### `serviceGroups.<name>.beforeStart`
+
+Shell command to run before starting the service group.
+
+**Type**:
+
+```console
+string
+```
+
+**Default value**:
+
+```nix
+""
+```
+
+**Declared in**:
+
+- [modules/services.nix](https://github.com/numtide/devshell/tree/main/modules/services.nix)
+
+### `serviceGroups.<name>.afterStart`
+
+Shell command to run after starting the service group.
+
+**Type**:
+
+```console
+string
+```
+
+**Default value**:
+
+```nix
+""
+```
+
+**Declared in**:
+
+- [modules/services.nix](https://github.com/numtide/devshell/tree/main/modules/services.nix)
+
+### `serviceGroups.<name>.beforeStop`
+
+Shell command to run before stopping the service group.
+
+**Type**:
+
+```console
+string
+```
+
+**Default value**:
+
+```nix
+""
+```
+
+**Declared in**:
+
+- [modules/services.nix](https://github.com/numtide/devshell/tree/main/modules/services.nix)
+
+### `serviceGroups.<name>.afterStop`
+
+Shell command to run after stopping the service group.
+
+**Type**:
+
+```console
+string
+```
+
+**Default value**:
+
+```nix
+""
+```
+
+**Declared in**:
+
+- [modules/services.nix](https://github.com/numtide/devshell/tree/main/modules/services.nix)
+
 ### `serviceGroups.<name>.services.<name>.command`
 
 Command to execute.

modules/services.nix

@@ -3,9 +3,9 @@
   lib,
   pkgs,
   ...
-}:
-let
-  inherit (lib)
+}: let
+  inherit
+    (lib)
     mkOption
     types
     ;
@@ -41,81 +41,125 @@ let
       '';
     };
     services = mkOption {
-      type = types.attrsOf (types.submodule { options = serviceOptions; });
-      default = { };
+      type = types.attrsOf (types.submodule {options = serviceOptions;});
+      default = {};
       description = ''
         Attrset of services that should be run in this group.
       '';
     };
+    beforeStart = mkOption {
+      type = types.lines;
+      default = "";
+      description = ''
+        Shell command to run before starting the service group.
+      '';
+    };
+    afterStart = mkOption {
+      type = types.lines;
+      default = "";
+      description = ''
+        Shell command to run after starting the service group.
+      '';
+    };
+    beforeStop = mkOption {
+      type = types.lines;
+      default = "";
+      description = ''
+        Shell command to run before stopping the service group.
+      '';
+    };
+    afterStop = mkOption {
+      type = types.lines;
+      default = "";
+      description = ''
+        Shell command to run after stopping the service group.
+      '';
+    };
   };
-  groupToProcfile =
-    name: g:
+  groupToProcfile = name: g:
     pkgs.writeText "Procfile.${name}" (
       lib.concatLines (
         lib.mapAttrsToList (
-          sName: s: "${if s.name == null then sName else s.name}: ${s.command}"
-        ) g.services
+          sName: s: "${
+            if s.name == null
+            then sName
+            else s.name
+          }: ${s.command}"
+        )
+        g.services
       )
     );
-  groupToCommands =
-    gName: g:
-    let
-      procfile = groupToProcfile gName g;
-      description = if g.description == null then gName else g.description;
-    in
-    [
-      {
-        name = "${gName}:start";
-        category = "service groups";
-        help = "Start ${description} services";
-        command =
-          (pkgs.writeShellScript "${gName}-services-start" ''
-            if [ -e "$PRJ_DATA_DIR/pids/${gName}.pid" ]; then
-              echo "Already running, refusing to start"
-              exit 1
-            fi
-            mkdir -p "$PRJ_DATA_DIR/pids/"
-            ${pkgs.honcho}/bin/honcho start -f ${procfile} -d "$PRJ_ROOT" &
-            pid=$!
-            echo $pid > "$PRJ_DATA_DIR/pids/${gName}.pid"
-            on_stop() {
-                if ps -p $pid > /dev/null; then
-                  kill -TERM $pid
-                fi
-                rm "$PRJ_DATA_DIR/pids/${gName}.pid"
-                wait $pid
-            }
-            trap "on_stop" SIGINT SIGTERM SIGHUP EXIT
-            wait $pid
-          '').outPath;
-      }
-      {
-        name = "${gName}:stop";
-        category = "service groups";
-        help = "Stop ${description} services";
-        command =
-          (pkgs.writeShellScript "${gName}-services-stop" ''
-            if [ -e "$PRJ_DATA_DIR/pids/${gName}.pid" ]; then
-              pid=$(${pkgs.coreutils}/bin/cat "$PRJ_DATA_DIR/pids/${gName}.pid")
-              kill -TERM $pid
+  groupToCommands = gName: g: let
+    procfile = groupToProcfile gName g;
+    description =
+      if g.description == null
+      then gName
+      else g.description;
+  in [
+    {
+      name = "${gName}:start";
+      category = "service groups";
+      help = "Start ${description} services";
+      command =
+        (pkgs.writeShellScript "${gName}-services-start" ''
+          if [ -e "$PRJ_DATA_DIR/pids/${gName}.pid" ]; then
+            echo "Already running, refusing to start"
+            exit 1
+          fi
+          mkdir -p "$PRJ_DATA_DIR/pids/"
+          ${g.beforeStart}
+          ${pkgs.honcho}/bin/honcho start -f ${procfile} -d "$PRJ_ROOT" &
+          pid=$!
+          echo $pid > "$PRJ_DATA_DIR/pids/${gName}.pid"
+          ${g.afterStart}
+          on_stop() {
+              ${g.beforeStop}
+              if ps -p $pid > /dev/null; then
+                kill -TERM $pid
+              fi
+              ${g.afterStop}
               rm "$PRJ_DATA_DIR/pids/${gName}.pid"
-            fi
-          '').outPath;
-      }
-    ];
-in
-{
+              wait $pid
+          }
+          trap "on_stop" SIGINT SIGTERM SIGHUP EXIT
+          wait $pid
+        '').outPath;
+    }
+    {
+      name = "${gName}:stop";
+      category = "service groups";
+      help = "Stop ${description} services";
+      command =
+        (pkgs.writeShellScript "${gName}-services-stop" ''
+          if [ -e "$PRJ_DATA_DIR/pids/${gName}.pid" ]; then
+            pid=$(${pkgs.coreutils}/bin/cat "$PRJ_DATA_DIR/pids/${gName}.pid")
+            ${g.beforeStop}
+            kill -TERM $pid
+            rm "$PRJ_DATA_DIR/pids/${gName}.pid"
+            ${g.afterStop}
+          fi
+        '').outPath;
+    }
+  ];
+in {
   options.serviceGroups = mkOption {
-    type = types.attrsOf (types.submodule { options = groupOptions; });
-    default = { };
+    type = types.attrsOf (types.submodule {options = groupOptions;});
+    default = {};
     description = ''
       Add services to the environment. Services can be used to group long-running processes.
     '';
   };
 
-  config.commands = lib.foldl (l: r: l ++ r) [ ] (
+  config.commands = lib.foldl (l: r: l ++ r) [] (
     lib.mapAttrsToList (
-      gName: g: groupToCommands (if g.name == null then gName else g.name) g
-    ) config.serviceGroups
+      gName: g:
+        groupToCommands (
+          if g.name == null
+          then gName
+          else g.name
+        )
+        g
+    )
+    config.serviceGroups
   );
 }