feat(registry): validate unique addresses and routes

lib/registry.nix

@@ -16,26 +16,37 @@ let
     nameValuePair
     removeSuffix
     types
+    unique
     ;
 
-  assertionType = types.submodule {
+  checkType = types.submodule {
     options = {
       assertion = mkOption {
-        type = types.bool;
+        type = types.functionTo types.bool;
         description = ''
-          Whether this registry validation assertion passed.
+          Predicate run against this registry's flattened collected entries.
         '';
       };
 
       message = mkOption {
         type = types.str;
         description = ''
-          Error message shown when this registry validation assertion fails.
+          Error message shown when this registry validation check fails.
         '';
       };
     };
   };
 
+  predicates = {
+    uniqueValue = value: entries: builtins.length (unique (map value entries)) == builtins.length entries;
+  };
+
+  registryLib = lib // {
+    registry = (lib.registry or { }) // {
+      inherit predicates;
+    };
+  };
+
   registryDefinitionModule = {
     options = {
       type = mkOption {
@@ -53,11 +64,11 @@ let
         '';
       };
 
-      validate = mkOption {
-        type = types.functionTo (types.listOf assertionType);
-        default = _entries: [ ];
+      checks = mkOption {
+        type = types.listOf checkType;
+        default = [ ];
         description = ''
-          Validate this registry's flattened collected entries.
+          Validation checks for this registry's flattened collected entries.
         '';
       };
     };
@@ -76,7 +87,7 @@ let
   mkRegistry = path:
     let
       evaluated = lib.evalModules {
-        specialArgs = { inherit lib; };
+        specialArgs.lib = registryLib;
         modules = [
           registryDefinitionModule
           path
@@ -84,7 +95,7 @@ let
       };
     in
     {
-      inherit (evaluated.config) type replicate validate;
+      inherit (evaluated.config) type replicate checks;
     };
 
   definitions = mapAttrs' (
@@ -149,7 +160,13 @@ let
     concatLists (
       mapAttrsToList (
         registryName: registry:
-        registry.validate (flattenRegistryEntries registryName data.${registryName})
+        let
+          entries = flattenRegistryEntries registryName data.${registryName};
+        in
+        map (check: {
+          assertion = check.assertion entries;
+          inherit (check) message;
+        }) registry.checks
       ) definitions
     );
 
@@ -189,7 +206,7 @@ let
     };
 in
 {
-  inherit definitions;
+  inherit definitions predicates;
 
   module = {
     options.registry = mapAttrs (_name: registry: registryOption registry) definitions;