nix: Add anvil state persistence for faster integration tests

Pin foundry to v1.4.0 and add state persistence options to anvil.nix:
- state: path to state file (loads on start, saves periodically)
- stateInterval: periodic state dump interval in seconds
- preserveHistoricalStates: keep historical states for older block queries

This allows anvil to persist blockchain state between test runs, skipping
contract deployment on subsequent runs. The state is saved every 30 seconds
to handle ungraceful shutdowns.

Author: lutter

flake.lock

@@ -1,7 +1,7 @@
 {
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
-    foundry.url = "github:shazow/foundry.nix";
+    foundry.url = "github:shazow/foundry.nix/b7adb89167832516589c899addcd25ca2a78dcfe";
     fenix = {
       url = "github:nix-community/fenix";
       inputs.nixpkgs.follows = "nixpkgs";
@@ -198,6 +198,9 @@
               gasLimit = 100000000000;
               baseFee = 1;
               blockTime = 2;
+              state = "./.data/integration/anvil/state.json";
+              stateInterval = 30;
+              preserveHistoricalStates = true;
             };
           };
         };

flake.nix

@@ -36,18 +36,62 @@
     };
 
     blockTime = lib.mkOption {
-      type = lib.types.int;
-      default = 2;
-      description = "Block time for the genesis block";
+      type = lib.types.nullOr lib.types.int;
+      default = null;
+      description = "Block time in seconds. Null means instant mining.";
+    };
+
+    state = lib.mkOption {
+      type = lib.types.nullOr lib.types.str;
+      default = null;
+      description = "Path to state file (loads on start, saves on exit)";
+    };
+
+    stateInterval = lib.mkOption {
+      type = lib.types.nullOr lib.types.int;
+      default = null;
+      description = "Interval in seconds to dump state to disk. Useful when graceful shutdown isn't guaranteed.";
+    };
+
+    preserveHistoricalStates = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = "Preserve historical state snapshots when dumping. Enables RPC calls for older blocks after state reload.";
     };
   };
 
   config = {
     outputs.settings.processes.${name} = {
-      command = "${lib.getExe' config.package "anvil"} --gas-limit ${toString config.gasLimit} --base-fee ${toString config.baseFee} --block-time ${toString config.blockTime} --timestamp ${toString config.timestamp} --port ${toString config.port}";
+      command = let
+        stateDir =
+          if config.state != null
+          then builtins.dirOf config.state
+          else null;
+        mkdirCmd =
+          if stateDir != null
+          then "mkdir -p ${stateDir} && "
+          else "";
+      in
+        mkdirCmd
+        + builtins.concatStringsSep " " (lib.filter (s: s != "") [
+          "${lib.getExe' config.package "anvil"}"
+          "--gas-limit ${toString config.gasLimit}"
+          "--base-fee ${toString config.baseFee}"
+          "--timestamp ${toString config.timestamp}"
+          "--port ${toString config.port}"
+          (lib.optionalString (config.blockTime != null) "--block-time ${toString config.blockTime}")
+          (lib.optionalString (config.state != null) "--state ${config.state}")
+          (lib.optionalString (config.stateInterval != null) "--state-interval ${toString config.stateInterval}")
+          (lib.optionalString config.preserveHistoricalStates "--preserve-historical-states")
+        ]);
 
       availability = {
-        restart = "always";
+        restart = "on_failure";
+      };
+
+      shutdown = {
+        command = "kill -TERM $${PROCESS_PID}";
+        timeout_seconds = 10;
       };
 
       readiness_probe = {