fix(deps): miette can now be used without syn (#436)

* style(clippy): quickly fix up clippy lints

* refactor(miette): remove `thiserror` from `error.rs`

* fix(fancy): `fancy` no longer depends on `derive`

Before this change, the `fancy` feature required the `derive` feature to
compile. Despite this, `derive` was not listed as a required feature to
use `fancy`. This meant that building with:
`cargo build --no-default-features --features fancy` would result in a
compilation error!

Now `fancy` can be used without `derive` enabled, and another use of
`thiserror` has been removed!

* refactor(miette): remove `thiserror` from `into_diagnostic.rs`

* refactor(miette): reuse `DiagnosticError` in `protocol.rs`

* refactor(miette): make `thiserror` a dev-dependency

* fix(miette): correctly forward error sources

* fix(miette): match `TestError` visibility with `mod tests`

* fix(miette): maintain 1.70 MSRV

* fix(miette): another fix for MSRV 1.70

* docs(miette): sync README and `rustdoc`

Cargo.toml

@@ -13,7 +13,6 @@ rust-version = "1.70.0"
 exclude = ["images/", "tests/", "miette-derive/"]
 
 [dependencies]
-thiserror = "2.0.11"
 miette-derive = { path = "miette-derive", version = "=7.5.0", optional = true }
 unicode-width = "0.1.11"
 cfg-if = "1.0.0"
@@ -30,6 +29,7 @@ serde = { version = "1.0.196", features = ["derive"], optional = true }
 syntect = { version = "5.1.0", optional = true }
 
 [dev-dependencies]
+thiserror = "2.0.11"
 semver = "1.0.21"
 
 # Eyre devdeps

src/error.rs

@@ -1,25 +1,51 @@
-use std::{fmt, io};
-
-use thiserror::Error;
+use std::{
+    error::Error,
+    fmt::{self, Display},
+    io,
+};
 
 use crate::Diagnostic;
 
 /**
 Error enum for miette. Used by certain operations in the protocol.
 */
-#[derive(Debug, Error)]
+#[derive(Debug)]
 pub enum MietteError {
     /// Wrapper around [`std::io::Error`]. This is returned when something went
     /// wrong while reading a [`SourceCode`](crate::SourceCode).
-    #[error(transparent)]
-    IoError(#[from] io::Error),
+    IoError(io::Error),
 
     /// Returned when a [`SourceSpan`](crate::SourceSpan) extends beyond the
     /// bounds of a given [`SourceCode`](crate::SourceCode).
-    #[error("The given offset is outside the bounds of its Source")]
     OutOfBounds,
 }
 
+impl Display for MietteError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            MietteError::IoError(error) => write!(f, "{error}"),
+            MietteError::OutOfBounds => {
+                write!(f, "The given offset is outside the bounds of its Source")
+            }
+        }
+    }
+}
+
+impl Error for MietteError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        match self {
+            MietteError::IoError(error) => error.source(),
+            MietteError::OutOfBounds => None,
+        }
+    }
+}
+
+impl From<io::Error> for MietteError {
+    fn from(value: io::Error) -> Self {
+        Self::IoError(value)
+    }
+}
+
 impl Diagnostic for MietteError {
     fn code<'a>(&'a self) -> Option<Box<dyn fmt::Display + 'a>> {
         match self {
@@ -49,3 +75,51 @@ impl Diagnostic for MietteError {
         )))
     }
 }
+
+#[cfg(test)]
+pub(crate) mod tests {
+    use std::{error::Error, io::ErrorKind};
+
+    use super::*;
+
+    #[derive(Debug)]
+    pub(crate) struct TestError(pub(crate) io::Error);
+
+    impl Display for TestError {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            write!(f, "testing, testing...")
+        }
+    }
+
+    impl Error for TestError {
+        fn source(&self) -> Option<&(dyn Error + 'static)> {
+            Some(&self.0)
+        }
+    }
+
+    #[test]
+    fn io_error() {
+        let inner_error = io::Error::new(ErrorKind::Other, "halt and catch fire");
+        let outer_error = TestError(inner_error);
+        let io_error = io::Error::new(ErrorKind::Other, outer_error);
+
+        let miette_error = MietteError::from(io_error);
+
+        assert_eq!(miette_error.to_string(), "testing, testing...");
+        assert_eq!(
+            miette_error.source().unwrap().to_string(),
+            "halt and catch fire"
+        );
+    }
+
+    #[test]
+    fn out_of_bounds() {
+        let miette_error = MietteError::OutOfBounds;
+
+        assert_eq!(
+            miette_error.to_string(),
+            "The given offset is outside the bounds of its Source"
+        );
+        assert_eq!(miette_error.source().map(ToString::to_string), None);
+    }
+}

src/eyreish/error.rs

@@ -280,7 +280,7 @@ impl Report {
     /// The root cause is the last error in the iterator produced by
     /// [`chain()`](Report::chain).
     pub fn root_cause(&self) -> &(dyn StdError + 'static) {
-        self.chain().last().unwrap()
+        self.chain().next_back().unwrap()
     }
 
     /// Returns true if `E` is the type held by this error object.

src/eyreish/into_diagnostic.rs

@@ -1,12 +1,24 @@
-use thiserror::Error;
+use std::{error::Error, fmt::Display};
 
 use crate::{Diagnostic, Report};
 
 /// Convenience [`Diagnostic`] that can be used as an "anonymous" wrapper for
 /// Errors. This is intended to be paired with [`IntoDiagnostic`].
-#[derive(Debug, Error)]
-#[error(transparent)]
+#[derive(Debug)]
 pub(crate) struct DiagnosticError(pub(crate) Box<dyn std::error::Error + Send + Sync + 'static>);
+
+impl Display for DiagnosticError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let msg = &self.0;
+        write!(f, "{msg}")
+    }
+}
+impl Error for DiagnosticError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        self.0.source()
+    }
+}
+
 impl Diagnostic for DiagnosticError {}
 
 /**
@@ -31,3 +43,26 @@ impl<T, E: std::error::Error + Send + Sync + 'static> IntoDiagnostic<T, E> for R
         self.map_err(|e| DiagnosticError(Box::new(e)).into())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::io::{self, ErrorKind};
+
+    use super::*;
+
+    use crate::error::tests::TestError;
+
+    #[test]
+    fn diagnostic_error() {
+        let inner_error = io::Error::new(ErrorKind::Other, "halt and catch fire");
+        let outer_error: Result<(), _> = Err(TestError(inner_error));
+
+        let diagnostic_error = outer_error.into_diagnostic().unwrap_err();
+
+        assert_eq!(diagnostic_error.to_string(), "testing, testing...");
+        assert_eq!(
+            diagnostic_error.source().unwrap().to_string(),
+            "halt and catch fire"
+        );
+    }
+}

src/handler.rs

@@ -424,7 +424,7 @@ impl HighlighterOption {
         highlighter: Option<MietteHighlighter>,
         supports_color: bool,
     ) -> HighlighterOption {
-        if color == Some(false) || (color == None && !supports_color) {
+        if color == Some(false) || (color.is_none() && !supports_color) {
             return HighlighterOption::Disable;
         }
         highlighter
@@ -433,6 +433,9 @@ impl HighlighterOption {
     }
 }
 
+// NOTE: This is manually implemented so that it's clearer what's going on with
+// the conditional compilation — clippy isn't picking up the `cfg` stuff here
+#[allow(clippy::derivable_impls)]
 impl Default for HighlighterOption {
     fn default() -> Self {
         cfg_if! {

src/highlighters/syntect.rs

@@ -96,12 +96,12 @@ impl SyntectHighlighter {
             }
         }
         // finally, attempt to guess syntax based on first line
-        return self.syntax_set.find_syntax_by_first_line(
+        self.syntax_set.find_syntax_by_first_line(
             std::str::from_utf8(contents.data())
                 .ok()?
                 .split('\n')
                 .next()?,
-        );
+        )
     }
 }
 
@@ -115,7 +115,7 @@ pub(crate) struct SyntectHighlighterState<'h> {
     use_bg_color: bool,
 }
 
-impl<'h> HighlighterState for SyntectHighlighterState<'h> {
+impl HighlighterState for SyntectHighlighterState<'_> {
     fn highlight_line<'s>(&mut self, line: &'s str) -> Vec<Styled<&'s str>> {
         if let Ok(ops) = self.parse_state.parse_line(line, self.syntax_set) {
             let use_bg_color = self.use_bg_color;

src/lib.rs

@@ -51,6 +51,7 @@
 //!   - [... handler options](#-handler-options)
 //!   - [... dynamic diagnostics](#-dynamic-diagnostics)
 //!   - [... syntax highlighting](#-syntax-highlighting)
+//!   - [... primary label](#-primary-label)
 //!   - [... collection of labels](#-collection-of-labels)
 //! - [Acknowledgements](#acknowledgements)
 //! - [License](#license)
@@ -690,6 +691,37 @@
 //! [`with_syntax_highlighting`](MietteHandlerOpts::with_syntax_highlighting)
 //! method. See the [`highlighters`] module docs for more details.
 //!
+//! ### ... primary label
+//!
+//! You can use the `primary` parameter to `label` to indicate that the label
+//! is the primary label.
+//!
+//! ```rust,ignore
+//! #[derive(Debug, Diagnostic, Error)]
+//! #[error("oops!")]
+//! struct MyError {
+//!     #[label(primary, "main issue")]
+//!     primary_span: SourceSpan,
+//!
+//!     #[label("other label")]
+//!     other_span: SourceSpan,
+//! }
+//! ```
+//!
+//! The `primary` parameter can be used at most once:
+//!
+//! ```rust,ignore
+//! #[derive(Debug, Diagnostic, Error)]
+//! #[error("oops!")]
+//! struct MyError {
+//!     #[label(primary, "main issue")]
+//!     primary_span: SourceSpan,
+//!
+//!     #[label(primary, "other label")] // Error: Cannot have more than one primary label.
+//!     other_span: SourceSpan,
+//! }
+//! ```
+//!
 //! ### ... collection of labels
 //!
 //! When the number of labels is unknown, you can use a collection of `SourceSpan`

src/panic.rs

@@ -1,7 +1,8 @@
-use backtrace::Backtrace;
-use thiserror::Error;
+use std::{error::Error, fmt::Display};
 
-use crate::{self as miette, Context, Diagnostic, Result};
+use backtrace::Backtrace;
+
+use crate::{Context, Diagnostic, Result};
 
 /// Tells miette to render panics using its rendering engine.
 pub fn set_panic_hook() {
@@ -25,11 +26,27 @@ pub fn set_panic_hook() {
     }));
 }
 
-#[derive(Debug, Error, Diagnostic)]
-#[error("{0}{panic}", panic = Panic::backtrace())]
-#[diagnostic(help("set the `RUST_BACKTRACE=1` environment variable to display a backtrace."))]
+#[derive(Debug)]
 struct Panic(String);
 
+impl Display for Panic {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let msg = &self.0;
+        let panic = Panic::backtrace();
+        write!(f, "{msg}{panic}")
+    }
+}
+
+impl Error for Panic {}
+
+impl Diagnostic for Panic {
+    fn help<'a>(&'a self) -> Option<Box<dyn Display + 'a>> {
+        Some(Box::new(
+            "set the `RUST_BACKTRACE=1` environment variable to display a backtrace.",
+        ))
+    }
+}
+
 impl Panic {
     fn backtrace() -> String {
         use std::fmt::Write;
@@ -84,3 +101,32 @@ impl Panic {
         "".into()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::error::Error;
+
+    use super::*;
+
+    #[test]
+    fn panic() {
+        let panic = Panic("ruh roh raggy".to_owned());
+
+        assert_eq!(panic.to_string(), "ruh roh raggy");
+        assert!(panic.source().is_none());
+        assert!(panic.code().is_none());
+        assert!(panic.severity().is_none());
+        assert_eq!(
+            panic.help().map(|h| h.to_string()),
+            Some(
+                "set the `RUST_BACKTRACE=1` environment variable to display a backtrace."
+                    .to_owned()
+            )
+        );
+        assert!(panic.url().is_none());
+        assert!(panic.source_code().is_none());
+        assert!(panic.labels().is_none());
+        assert!(panic.related().is_none());
+        assert!(panic.diagnostic_source().is_none());
+    }
+}

src/protocol.rs

@@ -12,7 +12,7 @@ use std::{
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
-use crate::MietteError;
+use crate::{DiagnosticError, MietteError};
 
 /// Adds rich metadata to your Error that can be used by
 /// [`Report`](crate::Report) to print really nice and human-friendly error
@@ -174,18 +174,7 @@ impl From<String> for Box<dyn Diagnostic + Send + Sync> {
 
 impl From<Box<dyn std::error::Error + Send + Sync>> for Box<dyn Diagnostic + Send + Sync> {
     fn from(s: Box<dyn std::error::Error + Send + Sync>) -> Self {
-        #[derive(thiserror::Error)]
-        #[error(transparent)]
-        struct BoxedDiagnostic(Box<dyn std::error::Error + Send + Sync>);
-        impl fmt::Debug for BoxedDiagnostic {
-            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-                fmt::Debug::fmt(&self.0, f)
-            }
-        }
-
-        impl Diagnostic for BoxedDiagnostic {}
-
-        Box::new(BoxedDiagnostic(s))
+        Box::new(DiagnosticError(s))
     }
 }