refactor: consolidate installer defaults and FILESYSTEM validation into config.sh

The installer had three sites touching FILESYSTEM: a top-level default in the monolith, a re-default block in gather_input, and a runtime validation block also in gather_input. The same scattering existed for LOCALE, KEYMAP, ENABLE_SSH, and NO_ENCRYPT. A future contributor changing one site wouldn't have known the other two existed.

Move all five defaults into the lib/config.sh declarations so config.sh is the single source of truth. Add validate_filesystem() in lib/config.sh and call it from main() between check_config and gather_input, so a typo in a config file's FILESYSTEM= fails fast before any install action runs.

The behavior change is stricter. An empty FILESYSTEM in a config file used to be silently defaulted to zfs, now it errors. Interactive mode is unaffected. select_filesystem still controls the value and already errored on cancellation.

Bats: 140 → 142. Five tests added in test_config.bats for the defaults pinning and validate_filesystem coverage. Three removed from test_archangel.bats for behavior that moved out of gather_input. Lint clean.

2 files changed, 55 insertions, 39 deletions

diff --git a/tests/unit/test_archangel.bats b/tests/unit/test_archangel.bats
index ccabec7..749f786 100644
--- a/tests/unit/test_archangel.bats
+++ b/tests/unit/test_archangel.bats
@@ -70,33 +70,9 @@ setup() {
 #############################
 # Optional-field defaults
 #############################
-
-@test "gather_input unattended defaults FILESYSTEM to zfs when empty" {
-    HOSTNAME=h
-    TIMEZONE=UTC
-    ROOT_PASSWORD=x
-    SELECTED_DISKS=(/dev/sda)
-    FILESYSTEM=""
-    NO_ENCRYPT=yes
-    gather_input >/dev/null
-    [ "$FILESYSTEM" = "zfs" ]
-}
-
-@test "gather_input unattended defaults LOCALE, KEYMAP, ENABLE_SSH when empty" {
-    HOSTNAME=h
-    TIMEZONE=UTC
-    ROOT_PASSWORD=x
-    SELECTED_DISKS=(/dev/sda)
-    FILESYSTEM=zfs
-    NO_ENCRYPT=yes
-    LOCALE=""
-    KEYMAP=""
-    ENABLE_SSH=""
-    gather_input >/dev/null
-    [ "$LOCALE" = "en_US.UTF-8" ]
-    [ "$KEYMAP" = "us" ]
-    [ "$ENABLE_SSH" = "yes" ]
-}
+# Default values themselves are pinned in test_config.bats (config.sh
+# is the single source of truth). The remaining test here covers the
+# adjacent guarantee: gather_input doesn't clobber values the user set.
 
 @test "gather_input unattended preserves explicit non-default values" {
     HOSTNAME=h
@@ -160,18 +136,9 @@ setup() {
 #############################
 # Filesystem validity
 #############################
-
-@test "gather_input unattended errors when FILESYSTEM is neither zfs nor btrfs" {
-    HOSTNAME=h
-    TIMEZONE=UTC
-    ROOT_PASSWORD=x
-    SELECTED_DISKS=(/dev/sda)
-    FILESYSTEM=ext4
-    NO_ENCRYPT=yes
-    run gather_input
-    [ "$status" -eq 1 ]
-    [[ "$output" == *"Invalid FILESYSTEM"* ]]
-}
+# Validation moved to validate_filesystem in lib/config.sh — covered
+# by test_config.bats. main() calls it between check_config and
+# gather_input so a bad FILESYSTEM= never reaches install time.
 
 #############################
 # RAID-level defaulting
diff --git a/tests/unit/test_config.bats b/tests/unit/test_config.bats
index c0c4e42..46f0236 100644
--- a/tests/unit/test_config.bats
+++ b/tests/unit/test_config.bats
@@ -156,3 +156,52 @@ EOF
     [ "$CONFIG_FILE" = "/tmp/foo.conf" ]
     [ -n "$RED" ]
 }
+
+#############################
+# Default values sourced from config.sh
+#############################
+# config.sh is the single source of truth for installer defaults. The
+# monolith no longer re-applies them in gather_input. These tests pin
+# the values so a regression that drops a default surfaces here, not
+# halfway through an unattended install.
+
+@test "config.sh sets defaults for FILESYSTEM, LOCALE, KEYMAP, ENABLE_SSH, NO_ENCRYPT" {
+    [ "$FILESYSTEM" = "zfs" ]
+    [ "$LOCALE" = "en_US.UTF-8" ]
+    [ "$KEYMAP" = "us" ]
+    [ "$ENABLE_SSH" = "yes" ]
+    [ "$NO_ENCRYPT" = "no" ]
+}
+
+#############################
+# validate_filesystem
+#############################
+# Called from main() between check_config and gather_input. Catches a
+# typo in FILESYSTEM= from a config file before the install starts.
+
+@test "validate_filesystem accepts zfs" {
+    FILESYSTEM=zfs
+    run validate_filesystem
+    [ "$status" -eq 0 ]
+}
+
+@test "validate_filesystem accepts btrfs" {
+    FILESYSTEM=btrfs
+    run validate_filesystem
+    [ "$status" -eq 0 ]
+}
+
+@test "validate_filesystem rejects an unknown filesystem" {
+    FILESYSTEM=ext4
+    run validate_filesystem
+    [ "$status" -eq 1 ]
+    [[ "$output" == *"Invalid FILESYSTEM"* ]]
+    [[ "$output" == *"ext4"* ]]
+}
+
+@test "validate_filesystem rejects an empty FILESYSTEM" {
+    FILESYSTEM=""
+    run validate_filesystem
+    [ "$status" -eq 1 ]
+    [[ "$output" == *"Invalid FILESYSTEM"* ]]
+}