Obviate writeShellApplication in 'command'

Author: srid

example/flake.nix

@@ -33,23 +33,17 @@
               '';
 
               # Create .sqlite database from chinook database.
-              sqlite-init.command = pkgs.writeShellApplication {
-                name = "sqlite-init";
-                text = ''
-                  echo "$(date): Importing Chinook database ($DATAFILE) ..."
-                  ${lib.getExe pkgs.sqlite} "$DATAFILE" < ${inputs.chinookDb}/ChinookDatabase/DataSources/Chinook_Sqlite.sql
-                  echo "$(date): Done."
-                '';
-              };
+              sqlite-init.command = ''
+                echo "$(date): Importing Chinook database ($DATAFILE) ..."
+                ${lib.getExe pkgs.sqlite} "$DATAFILE" < ${inputs.chinookDb}/ChinookDatabase/DataSources/Chinook_Sqlite.sql
+                echo "$(date): Done."
+              '';
 
               # Run sqlite-web on the local chinook database.
               sqlite-web = {
-                command = pkgs.writeShellApplication {
-                  name = "sqlite-web";
-                  text = ''
-                    ${pkgs.sqlite-web}/bin/sqlite_web "$DATAFILE"
-                  '';
-                };
+                command = ''
+                  ${pkgs.sqlite-web}/bin/sqlite_web "$DATAFILE"
+                '';
                 # The 'depends_on' will have this process wait until the above one is completed.
                 depends_on."sqlite-init".condition = "process_completed_successfully";
               };

nix/process-compose/settings/command.nix

@@ -1,9 +1,12 @@
-{ lib, ... }:
+{ name, pkgs, lib, ... }:
 
 args:
 lib.mkOption (args // {
   type = lib.types.either lib.types.package lib.types.str;
   apply = pkg:
-    if builtins.isString pkg then pkg else
-    lib.getExe pkg;
+    if builtins.isString pkg 
+      # process-compose is unreliable in handling environment variable, so let's
+      # wrap it in a bash script.
+      then lib.getExe (pkgs.writeShellApplication { inherit name; text = pkg; })
+      else lib.getExe pkg;
 })

nix/process-compose/settings/default.nix

@@ -52,14 +52,15 @@ in
               default = "-c";
               example = "-c";
             };
-            shell_command = import ./command.nix { inherit lib; } {
+            shell_command = mkOption {
+              type = types.str;
               description = ''
                 The shell to use to run the process `command`s.
 
                 For reproducibility across systems, by default this uses
                 `pkgs.bash`.
               '';
-              default = pkgs.bash;
+              default = lib.getExe pkgs.bash;
             };
           };
 

nix/process-compose/settings/process.nix

@@ -1,4 +1,4 @@
-{ lib, ... }:
+{ name, pkgs, lib, ... }:
 
 let
   inherit (lib) types mkOption;
@@ -9,12 +9,13 @@ let
 in
 {
   options = {
-    command = import ./command.nix { inherit lib; } {
+    command = import ./command.nix { inherit name pkgs lib; } {
       description = ''
-        The command that runs this process
+        The command or script or package that runs this process
 
-        If a package is given, its executable is used as the command. This is
-        useful to pass in a `writeShellApplication.`
+        If a package is given, its executable is used as the command. Otherwise,
+        the command string is wrapped in a `pkgs.writeShellApplication` which
+        uses ShellCheck and runs the command in bash.
       '';
     };
 

test/flake.nix

@@ -33,25 +33,19 @@
                     '';
                   };
                 in
-                pkgs.writeShellApplication {
-                  name = "sqlite-init";
-                  text = ''
-                    echo "$(date): Creating database ($DATAFILE) ..."
-                    ${lib.getExe pkgs.sqlite} "$DATAFILE" < ${sqlFile}
-                    echo "$(date): Done."
-                  '';
-                };
+                ''
+                  echo "$(date): Creating database ($DATAFILE) ..."
+                  ${lib.getExe pkgs.sqlite} "$DATAFILE" < ${sqlFile}
+                  echo "$(date): Done."
+                '';
 
               # Query something, write to result.txt
               sqlite-query = {
-                command = pkgs.writeShellApplication {
-                  name = "sqlite-query";
-                  text = ''
-                    ${lib.getExe pkgs.sqlite} "$DATAFILE" \
-                      'select val from demo where val = "Hello"' \
-                      > result.txt
-                  '';
-                };
+                command = ''
+                  ${lib.getExe pkgs.sqlite} "$DATAFILE" \
+                    'select val from demo where val = "Hello"' \
+                    > result.txt
+                '';
                 # The 'depends_on' will have this process wait until the above one is completed.
                 depends_on."sqlite-init".condition = "process_completed_successfully";
                 availability.restart = "no";