💥 Future-proof UnsupportedTerminal error

Author: bash

crates/benchmark/src/main.rs

@@ -42,7 +42,7 @@ fn main() -> Result<()> {
 
     let supported = match color_palette() {
         Ok(_) => true,
-        Err(Error::UnsupportedTerminal) => false,
+        Err(Error::UnsupportedTerminal(_)) => false,
         Err(e) => return Err(e),
     };
 
@@ -54,7 +54,7 @@ fn main() -> Result<()> {
 fn bench() -> Result<Duration> {
     let start = Instant::now();
     match black_box(color_palette()) {
-        Ok(_) | Err(Error::UnsupportedTerminal) => Ok(start.elapsed()),
+        Ok(_) | Err(Error::UnsupportedTerminal(_)) => Ok(start.elapsed()),
         Err(err) => Err(err),
     }
 }

crates/terminal-colorsaurus/src/error.rs

@@ -1,5 +1,6 @@
 use crate::fmt::CaretNotation;
 use core::fmt;
+use std::marker::PhantomData;
 use std::time::Duration;
 use std::{error, io};
 
@@ -16,13 +17,19 @@ pub enum Error {
     /// or the terminal has a lot of latency (e.g. when connected via SSH).
     Timeout(Duration),
     /// The terminal does not support querying for the foreground or background color.
-    UnsupportedTerminal,
+    UnsupportedTerminal(UnsupportedTerminalError),
 }
 
+// Note: the private field is here for fowards-compatibility
+// in case we want to introduce detailed reasons.
+#[derive(Debug)]
+pub struct UnsupportedTerminalError(PhantomData<()>);
+
 impl error::Error for Error {
     fn source(&self) -> Option<&(dyn error::Error + 'static)> {
         match self {
             Error::Io(source) => Some(source),
+            Error::UnsupportedTerminal(source) => Some(source),
             _ => None,
         }
     }
@@ -42,13 +49,25 @@ impl fmt::Display for Error {
             Error::Timeout(timeout) => {
                 write!(f, "operation did not complete within {timeout:?}")
             }
-            Error::UnsupportedTerminal {} => {
-                write!(f, "the terminal does not support querying for its colors")
-            }
+            Error::UnsupportedTerminal(e) => e.fmt(f),
         }
     }
 }
 
+impl Error {
+    pub(crate) fn unsupported() -> Self {
+        Error::UnsupportedTerminal(UnsupportedTerminalError(PhantomData))
+    }
+}
+
+impl error::Error for UnsupportedTerminalError {}
+
+impl fmt::Display for UnsupportedTerminalError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("the terminal does not support querying for its colors")
+    }
+}
+
 impl From<io::Error> for Error {
     fn from(source: io::Error) -> Self {
         Error::Io(source)

crates/terminal-colorsaurus/src/unsupported.rs

@@ -1,13 +1,13 @@
 use crate::{Color, ColorPalette, Error, QueryOptions, Result};
 
 pub(crate) fn color_palette(_options: QueryOptions) -> Result<ColorPalette> {
-    Err(Error::UnsupportedTerminal)
+    Err(Error::unsupported())
 }
 
 pub(crate) fn foreground_color(_options: QueryOptions) -> Result<Color> {
-    Err(Error::UnsupportedTerminal)
+    Err(Error::unsupported())
 }
 
 pub(crate) fn background_color(_options: QueryOptions) -> Result<Color> {
-    Err(Error::UnsupportedTerminal)
+    Err(Error::unsupported())
 }

crates/terminal-colorsaurus/src/xterm.rs

@@ -93,7 +93,7 @@ fn query<T>(
     read_response: impl FnOnce(&mut Reader<'_>) -> Result<T>,
 ) -> Result<T> {
     if quirks.is_known_unsupported() {
-        return Err(Error::UnsupportedTerminal);
+        return Err(Error::unsupported());
     }
 
     let mut tty = terminal()?;
@@ -123,7 +123,7 @@ fn read_color_response(r: &mut Reader<'_>) -> Result<Vec<u8>> {
     // the terminal does not recocgnize the color query.
     if !r.buffer().starts_with(b"]") {
         _ = consume_da1_response(r, false);
-        return Err(Error::UnsupportedTerminal);
+        return Err(Error::unsupported());
     }
 
     // Some terminals always respond with BEL (see terminal survey).