From e3d06c24e7a9e9582c70851f48468cb184e71012 Mon Sep 17 00:00:00 2001
From: Ana Hobden <operator@hoverbear.org>
Date: Fri, 10 Feb 2023 14:44:39 -0800
Subject: [PATCH] Offer users better error if fstab entries exist (#241)

* Offer users better error if fstab entries exist

* Split up errors

* Remove a naughty bracket

* last nits
---
 src/action/macos/create_fstab_entry.rs | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/action/macos/create_fstab_entry.rs b/src/action/macos/create_fstab_entry.rs
index e0980ab..106e87a 100644
--- a/src/action/macos/create_fstab_entry.rs
+++ b/src/action/macos/create_fstab_entry.rs
@@ -37,9 +37,18 @@ impl CreateFstabEntry {
                 .await
                 .map_err(|e| ActionError::Read(fstab_path.to_path_buf(), e))?;
             let prelude_comment = fstab_prelude_comment(&apfs_volume_label);
+
+            // See if the user already has a `/nix` related entry, if so, invite them to remove it.
+            if fstab_buf.split(&[' ', '\t']).any(|chunk| chunk == "/nix") {
+                return Err(ActionError::Custom(Box::new(
+                    CreateFstabEntryError::NixEntryExists,
+                )));
+            }
+
+            // See if a previous install from this crate exists, if so, invite the user to remove it (we may need to change it)
             if fstab_buf.contains(&prelude_comment) {
                 return Err(ActionError::Custom(Box::new(
-                    CreateFstabEntryError::EntryExists(apfs_volume_label.clone()),
+                    CreateFstabEntryError::VolumeEntryExists(apfs_volume_label.clone()),
                 )));
             }
         }
@@ -193,8 +202,10 @@ fn fstab_entry(uuid: &Uuid, apfs_volume_label: &str) -> String {
 
 #[derive(thiserror::Error, Debug)]
 pub enum CreateFstabEntryError {
-    #[error("An `/etc/fstab` entry for the volume labelled `{0}` already exists. If a Nix Store already exists it may need to be deleted with `diskutil apfs deleteVolume \"{0}\") and should be removed from `/etc/fstab`")]
-    EntryExists(String),
+    #[error("An `/etc/fstab` entry for the `/nix` path already exists, consider removing the entry for `/nix`d from `/etc/fstab`")]
+    NixEntryExists,
+    #[error("An `/etc/fstab` entry created by `nix-installer` already exists. If a volume named `{0}` already exists, it may need to be deleted with `diskutil apfs deleteVolume \"{0}\" and the entry for `/nix` should be removed from `/etc/fstab`")]
+    VolumeEntryExists(String),
 }
 
 #[derive(Deserialize, Clone, Debug)]