From 79eab0e82cb126bf4ac170f44af82479f0895ab5 Mon Sep 17 00:00:00 2001
From: Kira Bruneau <kira.bruneau@pm.me>
Date: Sun, 7 Apr 2024 16:49:23 -0400
Subject: [PATCH] types btrfs: fix format without swap or subvolumes

---
 example/btrfs-only-root-subvolume.nix | 37 +++++++++++++++++++++
 lib/types/btrfs.nix                   | 48 ++++++++++++++-------------
 tests/btrfs-only-root-subvolume.nix   | 11 ++++++
 3 files changed, 73 insertions(+), 23 deletions(-)
 create mode 100644 example/btrfs-only-root-subvolume.nix
 create mode 100644 tests/btrfs-only-root-subvolume.nix

diff --git a/example/btrfs-only-root-subvolume.nix b/example/btrfs-only-root-subvolume.nix
new file mode 100644
index 0000000..6a91656
--- /dev/null
+++ b/example/btrfs-only-root-subvolume.nix
@@ -0,0 +1,37 @@
+{
+  disko.devices = {
+    disk = {
+      vdb = {
+        type = "disk";
+        device = "/dev/disk/by-diskseq/1";
+        content = {
+          type = "gpt";
+          partitions = {
+            ESP = {
+              priority = 1;
+              name = "ESP";
+              start = "1M";
+              end = "128M";
+              type = "EF00";
+              content = {
+                type = "filesystem";
+                format = "vfat";
+                mountpoint = "/boot";
+              };
+            };
+            root = {
+              size = "100%";
+              content = {
+                type = "btrfs";
+                extraArgs = [ "-f" ]; # Override existing partition
+                mountpoint = "/";
+                mountOptions = [ "compress=zstd" "noatime" ];
+              };
+            };
+          };
+        };
+      };
+    };
+  };
+}
+
diff --git a/lib/types/btrfs.nix b/lib/types/btrfs.nix
index 0b32993..4b9fb6a 100644
--- a/lib/types/btrfs.nix
+++ b/lib/types/btrfs.nix
@@ -120,29 +120,31 @@ in
         if ! (blkid '${config.device}' -o export | grep -q '^TYPE='); then
           mkfs.btrfs "${config.device}" ${toString config.extraArgs}
         fi
-        if (blkid "${config.device}" -o export | grep -q '^TYPE=btrfs$'); then
-          ${lib.optionalString (config.swap != {}) ''
-            (
-              MNTPOINT=$(mktemp -d)
-              mount ${device} "$MNTPOINT" -o subvol=/
-              trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
-              ${swapCreate "$MNTPOINT" config.swap}
-            )
-          ''}
-          ${lib.concatMapStrings (subvol: ''
-            (
-              MNTPOINT=$(mktemp -d)
-              mount ${config.device} "$MNTPOINT" -o subvol=/
-              trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
-              SUBVOL_ABS_PATH="$MNTPOINT/${subvol.name}"
-              mkdir -p "$(dirname "$SUBVOL_ABS_PATH")"
-              if ! btrfs subvolume show "$SUBVOL_ABS_PATH" > /dev/null 2>&1; then
-                btrfs subvolume create "$SUBVOL_ABS_PATH" ${toString subvol.extraArgs}
-              fi
-              ${swapCreate "$SUBVOL_ABS_PATH" subvol.swap}
-            )
-          '') (lib.attrValues config.subvolumes)}
-        fi
+        ${lib.optionalString (config.swap != {} || config.subvolumes != {}) ''
+          if (blkid "${config.device}" -o export | grep -q '^TYPE=btrfs$'); then
+            ${lib.optionalString (config.swap != {}) ''
+              (
+                MNTPOINT=$(mktemp -d)
+                mount ${device} "$MNTPOINT" -o subvol=/
+                trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
+                ${swapCreate "$MNTPOINT" config.swap}
+              )
+            ''}
+            ${lib.concatMapStrings (subvol: ''
+              (
+                MNTPOINT=$(mktemp -d)
+                mount ${config.device} "$MNTPOINT" -o subvol=/
+                trap 'umount $MNTPOINT; rm -rf $MNTPOINT' EXIT
+                SUBVOL_ABS_PATH="$MNTPOINT/${subvol.name}"
+                mkdir -p "$(dirname "$SUBVOL_ABS_PATH")"
+                if ! btrfs subvolume show "$SUBVOL_ABS_PATH" > /dev/null 2>&1; then
+                  btrfs subvolume create "$SUBVOL_ABS_PATH" ${toString subvol.extraArgs}
+                fi
+                ${swapCreate "$SUBVOL_ABS_PATH" subvol.swap}
+              )
+            '') (lib.attrValues config.subvolumes)}
+          fi
+        ''}
       '';
     };
     _mount = diskoLib.mkMountOption {
diff --git a/tests/btrfs-only-root-subvolume.nix b/tests/btrfs-only-root-subvolume.nix
new file mode 100644
index 0000000..818aec7
--- /dev/null
+++ b/tests/btrfs-only-root-subvolume.nix
@@ -0,0 +1,11 @@
+{ pkgs ? import <nixpkgs> { }
+, diskoLib ? pkgs.callPackage ../lib { }
+}:
+diskoLib.testLib.makeDiskoTest {
+  inherit pkgs;
+  name = "btrfs-only-root-subvolume";
+  disko-config = ../example/btrfs-only-root-subvolume.nix;
+  extraTestScript = ''
+    machine.succeed("btrfs subvolume list /");
+  '';
+}