pkgs-lib/formats: add hcl1 format

pkgs/pkgs-lib/formats.nix

@@ -1053,4 +1053,27 @@ optionalAttrs allowAliases aliases
 
       generate = name: value: pkgs.writeText name (lib.generators.toPlist { inherit escape; } value);
     };
+
+  hcl1 =
+    args:
+    let
+      # Helper function to recursively transform values for HCL1 canonicalization
+      # Rule: If an attribute value is an attribute set, wrap it in a list
+      transform =
+        value:
+        if isAttrs value && !isDerivation value then
+          # If it's an attribute set, transform it recursively and wrap in a list
+          [ (mapAttrs (name: transform) value) ]
+        else if isList value then
+          # If it's already a list, transform each element
+          map transform value
+        else
+          value;
+      jsonFormat = json { };
+    in
+    jsonFormat
+    // {
+      generate = name: value: jsonFormat.generate name (mapAttrs (_: transform) value);
+    };
+
 }

pkgs/pkgs-lib/tests/formats.nix

@@ -1080,4 +1080,70 @@ runBuildTests {
       </dict>
       </plist>'';
   };
+
+  hcl1Atoms = shouldPass {
+    format = formats.hcl1 { };
+    input = {
+      resource = {
+        aws_instance = {
+          example = {
+            ami = "ami-12345";
+            instance_type = "t2.micro";
+          };
+        };
+      };
+      variable = {
+        region = {
+          default = "us-east-1";
+        };
+      };
+      output = {
+        ip = {
+          value = "127.0.0.1";
+        };
+      };
+      primitive = "just a string";
+      number = 42;
+      enabled = true;
+    };
+    expected = ''
+      {
+        "enabled": true,
+        "number": 42,
+        "output": [
+          {
+            "ip": [
+              {
+                "value": "127.0.0.1"
+              }
+            ]
+          }
+        ],
+        "primitive": "just a string",
+        "resource": [
+          {
+            "aws_instance": [
+              {
+                "example": [
+                  {
+                    "ami": "ami-12345",
+                    "instance_type": "t2.micro"
+                  }
+                ]
+              }
+            ]
+          }
+        ],
+        "variable": [
+          {
+            "region": [
+              {
+                "default": "us-east-1"
+              }
+            ]
+          }
+        ]
+      }
+    '';
+  };
 }