API(clanInternals): add 'evalServiceSchema' endpoint

lib/build-clan/interface.nix

@@ -174,6 +174,7 @@ in
           inventoryFile = lib.mkOption { type = lib.types.raw; };
           # The machine 'imports' generated by the inventory per machine
           inventoryClass = lib.mkOption { type = lib.types.raw; };
+          evalServiceSchema = lib.mkOption { };
           # clan-core's modules
           clanModules = lib.mkOption { type = lib.types.raw; };
           source = lib.mkOption { type = lib.types.raw; };

lib/build-clan/module.nix

@@ -205,6 +205,21 @@ in
 
     inherit inventoryClass;
 
+    # Endpoint that can be called to get a service schema
+    evalServiceSchema =
+      {moduleSpec}:
+      let
+        resolvedModule = clan-core.clanLib.inventory.resolveModule {
+          inherit moduleSpec;
+          flakeInputs = config.self.inputs;
+          localModuleSet = config.inventory.modules;
+        };
+      in
+      (clan-core.clanLib.inventory.evalClanService {
+        modules = [ resolvedModule ];
+        prefix = [ ];
+      }).config.result.api.schema;
+
     # TODO: unify this interface
     # We should have only clan.modules. (consistent with clan.templates)
     inherit (clan-core) clanModules clanLib;

lib/inventory/default.nix

@@ -3,7 +3,7 @@ let
   services = clanLib.callLib ./distributed-service/inventory-adapter.nix { };
 in
 {
-  inherit (services) evalClanService mapInstances;
+  inherit (services) evalClanService mapInstances resolveModule;
   inherit (import ./build-inventory { inherit lib clanLib; }) buildInventory;
   interface = ./build-inventory/interface.nix;
   # Returns the list of machine names

lib/inventory/distributed-service/inventory-adapter.nix

@@ -27,9 +27,53 @@ let
         })
       ] ++ modules;
     });
+
+  resolveModule =
+    {
+      moduleSpec,
+      flakeInputs,
+      localModuleSet,
+    }:
+    let
+      # TODO:
+      resolvedModuleSet =
+        # If the module.name is self then take the modules defined in the flake
+        # Otherwise its an external input which provides the modules via 'clan.modules' attribute
+        if moduleSpec.input == null then
+          localModuleSet
+        else
+          let
+            input =
+              flakeInputs.${moduleSpec.input} or (throw ''
+                Flake doesn't provide input with name '${moduleSpec.input}'
+
+                Choose one of the following inputs:
+                - ${
+                  builtins.concatStringsSep "\n- " (
+                    lib.attrNames (lib.filterAttrs (_name: input: input ? clan) flakeInputs)
+                  )
+                }
+
+                To import a local module from 'inventory.modules' remove the 'input' attribute from the module definition
+                Remove the following line from the module definition:
+
+                ...
+                - module.input = "${moduleSpec.input}"
+
+              '');
+            clanAttrs =
+              input.clan or (throw "It seems the flake input ${moduleSpec.input} doesn't export any clan resources");
+          in
+          clanAttrs.modules;
+
+      resolvedModule =
+        resolvedModuleSet.${moduleSpec.name}
+          or (throw "flake doesn't provide clan-module with name ${moduleSpec.name}");
+    in
+    resolvedModule;
 in
 {
-  inherit evalClanService;
+  inherit evalClanService resolveModule;
   mapInstances =
     {
       # This is used to resolve the module imports from 'flake.inputs'
@@ -45,42 +89,11 @@ in
       importedModuleWithInstances = lib.mapAttrs (
         instanceName: instance:
         let
-          # TODO:
-          resolvedModuleSet =
-            # If the module.name is self then take the modules defined in the flake
-            # Otherwise its an external input which provides the modules via 'clan.modules' attribute
-            if instance.module.input == null then
-              inventory.modules
-            else
-              let
-                input =
-                  flakeInputs.${instance.module.input} or (throw ''
-                    Flake doesn't provide input with name '${instance.module.input}'
-
-                    Choose one of the following inputs:
-                    - ${
-                      builtins.concatStringsSep "\n- " (
-                        lib.attrNames (lib.filterAttrs (_name: input: input ? clan) flakeInputs)
-                      )
-                    }
-
-                    To import a local module from 'inventory.modules' remove the 'input' attribute from the module definition
-                    Remove the following line from the module definition:
-
-                    ...
-                    - module.input = "${instance.module.input}"
-
-
-                  '');
-                clanAttrs =
-                  input.clan
-                    or (throw "It seems the flake input ${instance.module.input} doesn't export any clan resources");
-              in
-              clanAttrs.modules;
-
-          resolvedModule =
-            resolvedModuleSet.${instance.module.name}
-              or (throw "flake doesn't provide clan-module with name ${instance.module.name}");
+          resolvedModule = resolveModule {
+            moduleSpec = instance.module;
+            localModuleSet = inventory.modules;
+            inherit flakeInputs;
+          };
 
           # Every instance includes machines via roles
           # :: { client :: ... }