From 29e5515132e5f312f4a3c052b94330644b2ee12b Mon Sep 17 00:00:00 2001
From: Sai Asish Y <say.apm35@gmail.com>
Date: Sun, 16 Aug 2026 02:28:22 -0700
Subject: [PATCH 1/2] fix(config-traits): open read-only config files without
 panicking

Signed-off-by: Sai Asish Y <say.apm35@gmail.com>
---
 config-traits/src/lib.rs | 55 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 52 insertions(+), 3 deletions(-)

diff --git a/config-traits/src/lib.rs b/config-traits/src/lib.rs
index c5b1bd29a..de53706b7 100644
--- a/config-traits/src/lib.rs
+++ b/config-traits/src/lib.rs
@@ -83,15 +83,25 @@ where
 
     /// Directly open the config file for read and write. If the config file
     /// does not exist it is created, including the directories the file
-    /// resides in.
+    /// resides in. If the file exists but is not writable (e.g. a symlink into
+    /// a read-only store) it is opened read-only instead.
     fn file_open(&self) -> File {
+        let path = self.file_path();
         OpenOptions::new()
             .read(true)
             .write(true)
             .create(true)
             .truncate(false)
-            .open(self.file_path())
-            .unwrap_or_else(|e| panic!("Could not open {:?} {e}", self.file_path()))
+            .open(&path)
+            .or_else(|e| {
+                if e.kind() == std::io::ErrorKind::PermissionDenied && path.exists() {
+                    warn!("Config {path:?} is not writable, opening read-only: {e}");
+                    File::open(&path)
+                } else {
+                    Err(e)
+                }
+            })
+            .unwrap_or_else(|e| panic!("Could not open {:?} {e}", path))
     }
 
     /// Open and parse the config file to self from ron format
@@ -254,6 +264,45 @@ std_config_load!(StdConfigLoad4: T1, T2, T3, T4);
 mod tests {
     use std::path::PathBuf;
 
+    #[test]
+    fn load_read_only_config() {
+        use crate::{StdConfig, StdConfigLoad};
+
+        #[derive(serde::Deserialize, serde::Serialize, Debug)]
+        struct Test {
+            value: u32,
+        }
+
+        impl crate::StdConfig for Test {
+            fn new() -> Self {
+                Self { value: 0 }
+            }
+
+            fn file_name(&self) -> String {
+                "read_only_test.ron".to_owned()
+            }
+
+            fn config_dir() -> PathBuf {
+                std::env::temp_dir().join("config_traits_read_only_test")
+            }
+        }
+
+        impl crate::StdConfigLoad for Test {}
+
+        let dir = Test::config_dir();
+        std::fs::create_dir_all(&dir).unwrap();
+        let path = dir.join("read_only_test.ron");
+        std::fs::write(&path, "(value: 7)").unwrap();
+        let mut perms = std::fs::metadata(&path).unwrap().permissions();
+        perms.set_readonly(true);
+        std::fs::set_permissions(&path, perms).unwrap();
+
+        let cfg = Test::new().load();
+        assert_eq!(cfg.value, 7);
+
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
     #[test]
     fn check_macro_from_1() {
         #[derive(serde::Deserialize, serde::Serialize, Debug)]

From 65c8b3f2f34679c1ddf9153d0a8fe1b70cdf987a Mon Sep 17 00:00:00 2001
From: Sai Asish Y <say.apm35@gmail.com>
Date: Sat, 22 Aug 2026 23:21:10 -0700
Subject: [PATCH 2/2] fix(config-traits): also fall back to read-only on
 ReadOnlyFilesystem

Signed-off-by: Sai Asish Y <say.apm35@gmail.com>
---
 config-traits/src/lib.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/config-traits/src/lib.rs b/config-traits/src/lib.rs
index de53706b7..c991519c9 100644
--- a/config-traits/src/lib.rs
+++ b/config-traits/src/lib.rs
@@ -84,7 +84,8 @@ where
     /// Directly open the config file for read and write. If the config file
     /// does not exist it is created, including the directories the file
     /// resides in. If the file exists but is not writable (e.g. a symlink into
-    /// a read-only store) it is opened read-only instead.
+    /// a read-only store, which reports either `PermissionDenied` or
+    /// `ReadOnlyFilesystem`) it is opened read-only instead.
     fn file_open(&self) -> File {
         let path = self.file_path();
         OpenOptions::new()
@@ -94,7 +95,12 @@ where
             .truncate(false)
             .open(&path)
             .or_else(|e| {
-                if e.kind() == std::io::ErrorKind::PermissionDenied && path.exists() {
+                let kind = e.kind();
+                if matches!(
+                    kind,
+                    std::io::ErrorKind::PermissionDenied | std::io::ErrorKind::ReadOnlyFilesystem
+                ) && path.exists()
+                {
                     warn!("Config {path:?} is not writable, opening read-only: {e}");
                     File::open(&path)
                 } else {