From b5683029f90759425ee919afa359e618f57f127b Mon Sep 17 00:00:00 2001
From: Magic_RB <magic_rb@redalder.org>
Date: Tue, 7 Jun 2022 23:19:09 +0200
Subject: [PATCH] Add option to substitute on the target machine if local build

Signed-off-by: Magic_RB <magic_rb@redalder.org>

Co-authored-by: matthewcroughan <matt@croughan.sh>
---
 README.md | 8 ++++++++
 flake.nix | 5 +++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 74f032e..4aadffb 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,7 @@ Below is a minimal example:
               host = "itchy.scratchy.com";
               sshUser = "matthew";
               buildOn = "remote"; # valid args are "local" or "remote"
+              substituteOnTarget = true; # if buildOn is "local" then it will substitute on the target, "-s"
               hermetic = false;
             };
           }
@@ -105,6 +106,13 @@ Connection to itchy.scratchy.com closed.
   Whether to copy Nix to the remote for usage when building and activating,
   instead of using the Nix which is already installed on the remote.
 
+- `substituteOnTarget` *`bool`*
+
+  Whether to fetch closures and paths from the remote, even when building
+  locally. This makes sense in most cases, because the remote will have already
+  built a lot of the paths from the previous deployment. However, if the remote
+  has a slow upload bandwidth, this would not be a good idea to enable.
+
 # Project Principles
 
 * No Premature Optimization: Make it work, then optimize it later if the
diff --git a/flake.nix b/flake.nix
index c061db3..fb448c6 100644
--- a/flake.nix
+++ b/flake.nix
@@ -27,7 +27,7 @@
             validMachines = final.lib.remove "" (final.lib.forEach machines (x: final.lib.optionalString (flake.nixosConfigurations."${x}"._module.args ? nixinate) "${x}" ));
             mkDeployScript = { machine, dryRun }: let
               inherit (builtins) abort;
-              inherit (final.lib) getExe;
+              inherit (final.lib) getExe optionalString;
               nix = "${getExe final.nix}";
               nixos-rebuild = "${getExe final.nixos-rebuild}";
               openssh = "${getExe final.openssh}";
@@ -38,6 +38,7 @@
               host = n.host;
               where = n.buildOn or "remote";
               remote = if where == "remote" then true else if where == "local" then false else abort "_module.args.nixinate.buildOn is not set to a valid value of 'local' or 'remote'";
+              substituteOnTarget = n.substituteOnTarget or false;
               switch = if dryRun then "dry-activate" else "switch";
               script =
               ''
@@ -58,7 +59,7 @@
               '')
               else ''
                 echo "🔨 Building system closure locally, copying it to remote store and activating it:"
-                ( set -x; NIX_SSHOPTS="-t" ${nixos-rebuild} ${switch} --flake ${flake}#${machine} --target-host ${user}@${host} --use-remote-sudo )
+                ( set -x; NIX_SSHOPTS="-t" ${nixos-rebuild} ${switch} --flake ${flake}#${machine} --target-host ${user}@${host} --use-remote-sudo ${optionalString substituteOnTarget "-s"} )
               '');
             in final.writeScript "deploy-${machine}.sh" script;
           in
-- 
2.45.3