fix: doctor lists errors on one line with the hint last

src/doctor.rs

@@ -4,6 +4,7 @@ use std::path::Path;
 use anyhow::{Result, bail};
 
 use crate::config;
+use crate::error::one_line;
 use crate::niri;
 use crate::wayland::Wayland;
 
@@ -96,7 +97,10 @@ pub fn check_niri(version: Result<String>) -> Check {
     match version {
         Err(e) => check(
             Level::Warn,
-            format!("niri IPC unavailable ({e:#}); using the first output for `screen`"),
+            format!(
+                "niri IPC unavailable ({}); using the first output for `screen`",
+                one_line(&e)
+            ),
         ),
         Ok(v) => match niri::parse_version(&v) {
             Some(found) if found == niri::IPC_VERSION => check(Level::Ok, format!("niri {v}")),
@@ -117,7 +121,7 @@ pub fn check_config(path: &Path) -> Check {
             Level::Ok,
             format!("config {} not found, using defaults", path.display()),
         ),
-        Err(e) => check(Level::Fail, format!("config: {e:#}")),
+        Err(e) => check(Level::Fail, format!("config: {}", one_line(&e))),
     }
 }
 
@@ -155,7 +159,7 @@ pub fn run() -> Result<()> {
                 ));
             }
         }
-        Err(e) => checks.push(check(Level::Fail, format!("wayland: {e:#}"))),
+        Err(e) => checks.push(check(Level::Fail, format!("wayland: {}", one_line(&e)))),
     }
     checks.push(check_niri(niri::version()));
     let config_path = config::default_path();
@@ -246,6 +250,26 @@ mod tests {
         );
     }
 
+    #[test]
+    fn broken_config_fails_with_hint_last() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("config.toml");
+        std::fs::write(&path, "[save]\ndirectory = \n").unwrap();
+        let c = check_config(&path);
+        assert_eq!(c.level, Level::Fail);
+        assert!(
+            c.text.starts_with("config: invalid config file"),
+            "{}",
+            c.text
+        );
+        assert!(
+            c.text
+                .ends_with("(hint: fix the file or delete it to use the defaults)"),
+            "{}",
+            c.text
+        );
+    }
+
     #[test]
     fn save_dir_checks() {
         let dir = tempfile::tempdir().unwrap();

src/error.rs

@@ -58,6 +58,22 @@ pub fn render(err: &anyhow::Error, log: Option<&Path>) -> String {
     out
 }
 
+/// The error on one line, hint last: `msg: cause (hint: ...)`. For places
+/// that list several results, like `valw doctor`.
+pub fn one_line(err: &anyhow::Error) -> String {
+    let hint = err.downcast_ref::<Hint>().map(|h| h.0.as_str());
+    let messages: Vec<String> = err
+        .chain()
+        .map(|e| e.to_string())
+        .filter(|m| Some(m.as_str()) != hint)
+        .collect();
+    let mut out = messages.join(": ");
+    if let Some(hint) = hint {
+        out.push_str(&format!(" (hint: {hint})"));
+    }
+    out
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -101,6 +117,19 @@ mod tests {
         );
     }
 
+    #[test]
+    fn one_line_puts_hint_last() {
+        let err = Err::<(), _>(anyhow!("Could not find wayland compositor"))
+            .context("could not connect to the Wayland compositor")
+            .hint("valw needs a Wayland session; is WAYLAND_DISPLAY set?")
+            .unwrap_err();
+        assert_eq!(
+            one_line(&err),
+            "could not connect to the Wayland compositor: Could not find wayland compositor \
+             (hint: valw needs a Wayland session; is WAYLAND_DISPLAY set?)"
+        );
+    }
+
     #[test]
     fn cancelled_is_detectable() {
         let err = anyhow::Error::new(Cancelled).context("region selection");