Don't modify shell profile files if they are symlinks (#767)

* Don't modify shell profile files if they are symlinks

* Fixup remote building step

src/action/common/configure_shell_profile.rs

@@ -44,6 +44,8 @@ impl ConfigureShellProfile {
         for profile_target in locations.bash.iter().chain(locations.zsh.iter()) {
             let profile_target_path = Path::new(profile_target);
             if let Some(parent) = profile_target_path.parent() {
+                // Some tools (eg `nix-darwin`) create symlinks to these files, don't write to them if that's the case.
+                if !profile_target_path.is_symlink() {
                     if !parent.exists() {
                         create_directories.push(
                             CreateDirectory::plan(parent, None, None, 0o0755, false)
@@ -51,6 +53,7 @@ impl ConfigureShellProfile {
                                 .map_err(Self::error)?,
                         );
                     }
+
                     create_or_insert_files.push(
                         CreateOrInsertIntoFile::plan(
                             profile_target_path,
@@ -65,6 +68,7 @@ impl ConfigureShellProfile {
                     );
                 }
             }
+        }
 
         let fish_buf = format!(
             "\n\
@@ -88,9 +92,12 @@ impl ConfigureShellProfile {
             let mut profile_target = fish_prefix_path;
             profile_target.push(locations.fish.confd_suffix.clone());
 
+            // Some tools (eg `nix-darwin`) create symlinks to these files, don't write to them if that's the case.
+            if !profile_target.is_symlink() {
                 if let Some(conf_d) = profile_target.parent() {
                     create_directories.push(
-                    CreateDirectory::plan(conf_d.to_path_buf(), None, None, 0o755, false).await?,
+                        CreateDirectory::plan(conf_d.to_path_buf(), None, None, 0o755, false)
+                            .await?,
                     );
                 }
 
@@ -106,6 +113,7 @@ impl ConfigureShellProfile {
                     .await?,
                 );
             }
+        }
         for fish_prefix in &locations.fish.vendor_confd_prefixes {
             let fish_prefix_path = PathBuf::from(fish_prefix);
 

src/action/macos/configure_remote_building.rs

@@ -12,7 +12,7 @@ This enables remote building, which requires `ssh host nix` to work.
  */
 #[derive(Debug, serde::Deserialize, serde::Serialize, Clone)]
 pub struct ConfigureRemoteBuilding {
-    create_or_insert_into_file: StatefulAction<CreateOrInsertIntoFile>,
+    create_or_insert_into_file: Option<StatefulAction<CreateOrInsertIntoFile>>,
 }
 
 impl ConfigureRemoteBuilding {
@@ -29,8 +29,12 @@ fi
 "#
         );
 
-        let create_or_insert_into_file = CreateOrInsertIntoFile::plan(
+        let zshenv = Path::new("/etc/zshenv");
-            Path::new("/etc/zshenv"),
+
+        let create_or_insert_into_file = if !zshenv.is_symlink() {
+            Some(
+                CreateOrInsertIntoFile::plan(
+                    zshenv,
                     None,
                     None,
                     0o644,
@@ -38,7 +42,11 @@ fi
                     create_or_insert_into_file::Position::Beginning,
                 )
                 .await
-        .map_err(Self::error)?;
+                .map_err(Self::error)?,
+            )
+        } else {
+            None
+        };
 
         Ok(Self {
             create_or_insert_into_file,
@@ -63,7 +71,11 @@ impl Action for ConfigureRemoteBuilding {
 
     fn execute_description(&self) -> Vec<ActionDescription> {
         vec![ActionDescription::new(
-            self.tracing_synopsis(),
+            if self.create_or_insert_into_file.is_none() {
+                "Skipping configuring zsh to support using Nix in non-interactive shells, `/etc/zshenv` is a symlink".to_string()
+            } else {
+                self.tracing_synopsis()
+            },
             vec!["Update `/etc/zshenv` to import Nix".to_string()],
         )]
     }
@@ -71,11 +83,13 @@ impl Action for ConfigureRemoteBuilding {
     #[tracing::instrument(level = "debug", skip_all)]
     async fn execute(&mut self) -> Result<(), ActionError> {
         let span = tracing::Span::current().clone();
-        self.create_or_insert_into_file
+        if let Some(create_or_insert_into_file) = &mut self.create_or_insert_into_file {
+            create_or_insert_into_file
                 .try_execute()
                 .instrument(span)
                 .await
                 .map_err(Self::error)?;
+        }
 
         Ok(())
     }
@@ -89,7 +103,9 @@ impl Action for ConfigureRemoteBuilding {
 
     #[tracing::instrument(level = "debug", skip_all)]
     async fn revert(&mut self) -> Result<(), ActionError> {
-        self.create_or_insert_into_file.try_revert().await?;
+        if let Some(create_or_insert_into_file) = &mut self.create_or_insert_into_file {
+            create_or_insert_into_file.try_revert().await?
+        };
 
         Ok(())
     }