feat(graphical): Allow miette users to opt-out of the rendering of the cause chain (#192)

Fixes: https://github.com/zkat/miette/issues/191

src/handler.rs

@@ -56,6 +56,7 @@ pub struct MietteHandlerOpts {
     pub(crate) footer: Option<String>,
     pub(crate) context_lines: Option<usize>,
     pub(crate) tab_width: Option<usize>,
+    pub(crate) with_cause_chain: Option<bool>,
 }
 
 impl MietteHandlerOpts {
@@ -87,6 +88,18 @@ impl MietteHandlerOpts {
         self
     }
 
+    /// Include the cause chain of the top-level error in the report.
+    pub fn with_cause_chain(mut self) -> Self {
+        self.with_cause_chain = Some(true);
+        self
+    }
+
+    /// Do not include the cause chain of the top-level error in the report.
+    pub fn without_cause_chain(mut self) -> Self {
+        self.with_cause_chain = Some(false);
+        self
+    }
+
     /// If true, colors will be used during graphical rendering, regardless
     /// of whether or not the terminal supports them.
     ///
@@ -165,6 +178,13 @@ impl MietteHandlerOpts {
             if let Some(context_lines) = self.context_lines {
                 handler = handler.with_context_lines(context_lines);
             }
+            if let Some(with_cause_chain) = self.with_cause_chain {
+                if with_cause_chain {
+                    handler = handler.with_cause_chain();
+                } else {
+                    handler = handler.without_cause_chain();
+                }
+            }
             MietteHandler {
                 inner: Box::new(handler),
             }
@@ -197,6 +217,13 @@ impl MietteHandlerOpts {
                 .with_width(width)
                 .with_links(linkify)
                 .with_theme(theme);
+            if let Some(with_cause_chain) = self.with_cause_chain {
+                if with_cause_chain {
+                    handler = handler.with_cause_chain();
+                } else {
+                    handler = handler.without_cause_chain();
+                }
+            }
             if let Some(footer) = self.footer {
                 handler = handler.with_footer(footer);
             }

src/handlers/graphical.rs

@@ -28,6 +28,7 @@ pub struct GraphicalReportHandler {
     pub(crate) footer: Option<String>,
     pub(crate) context_lines: usize,
     pub(crate) tab_width: Option<usize>,
+    pub(crate) with_cause_chain: bool,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -48,6 +49,7 @@ impl GraphicalReportHandler {
             footer: None,
             context_lines: 1,
             tab_width: None,
+            with_cause_chain: true,
         }
     }
 
@@ -60,6 +62,7 @@ impl GraphicalReportHandler {
             footer: None,
             context_lines: 1,
             tab_width: None,
+            with_cause_chain: true,
         }
     }
 
@@ -79,6 +82,20 @@ impl GraphicalReportHandler {
         self
     }
 
+    /// Include the cause chain of the top-level error in the graphical output,
+    /// if available.
+    pub fn with_cause_chain(mut self) -> Self {
+        self.with_cause_chain = true;
+        self
+    }
+
+    /// Do not include the cause chain of the top-level error in the graphical
+    /// output.
+    pub fn without_cause_chain(mut self) -> Self {
+        self.with_cause_chain = false;
+        self
+    }
+
     /// Whether to include [`Diagnostic::url()`] in the output.
     ///
     /// Disabling this is not recommended, but can be useful for more easily
@@ -199,6 +216,10 @@ impl GraphicalReportHandler {
 
         writeln!(f, "{}", textwrap::fill(&diagnostic.to_string(), opts))?;
 
+        if !self.with_cause_chain {
+            return Ok(());
+        }
+
         if let Some(mut cause_iter) = diagnostic
             .diagnostic_source()
             .map(DiagnosticChain::from_diagnostic)

src/handlers/narratable.rs

@@ -14,6 +14,7 @@ non-graphical environments, such as non-TTY output.
 #[derive(Debug, Clone)]
 pub struct NarratableReportHandler {
     context_lines: usize,
+    with_cause_chain: bool,
     footer: Option<String>,
 }
 
@@ -24,9 +25,23 @@ impl NarratableReportHandler {
         Self {
             footer: None,
             context_lines: 1,
+            with_cause_chain: true,
         }
     }
 
+    /// Include the cause chain of the top-level error in the report, if
+    /// available.
+    pub fn with_cause_chain(mut self) -> Self {
+        self.with_cause_chain = true;
+        self
+    }
+
+    /// Do not include the cause chain of the top-level error in the report.
+    pub fn without_cause_chain(mut self) -> Self {
+        self.with_cause_chain = false;
+        self
+    }
+
     /// Set the footer to be displayed at the end of the report.
     pub fn with_footer(mut self, footer: String) -> Self {
         self.footer = Some(footer);
@@ -57,7 +72,9 @@ impl NarratableReportHandler {
         diagnostic: &(dyn Diagnostic),
     ) -> fmt::Result {
         self.render_header(f, diagnostic)?;
-        self.render_causes(f, diagnostic)?;
+        if self.with_cause_chain {
+            self.render_causes(f, diagnostic)?;
+        }
         let src = diagnostic.source_code();
         self.render_snippets(f, diagnostic, src)?;
         self.render_footer(f, diagnostic)?;

src/lib.rs

@@ -582,15 +582,14 @@
 //! `miette` was not developed in a void. It owes enormous credit to various
 //! other projects and their authors:
 //!
-//! - [`anyhow`](http://crates.io/crates/anyhow) and
-//!   [`color-eyre`](https://crates.io/crates/color-eyre): these two
-//!   enormously influential error handling libraries have pushed forward the
-//!   experience of application-level error handling and error reporting.
-//!   `miette`'s `Report` type is an attempt at a very very rough version of
-//!   their `Report` types.
-//! - [`thiserror`](https://crates.io/crates/thiserror) for setting the
-//!   standard for library-level error definitions, and for being the
-//!   inspiration behind `miette`'s derive macro.
+//! - [`anyhow`](http://crates.io/crates/anyhow) and [`color-eyre`](https://crates.io/crates/color-eyre):
+//!   these two enormously influential error handling libraries have pushed
+//!   forward the experience of application-level error handling and error
+//!   reporting. `miette`'s `Report` type is an attempt at a very very rough
+//!   version of their `Report` types.
+//! - [`thiserror`](https://crates.io/crates/thiserror) for setting the standard
+//!   for library-level error definitions, and for being the inspiration behind
+//!   `miette`'s derive macro.
 //! - `rustc` and [@estebank](https://github.com/estebank) for their
 //!   state-of-the-art work in compiler diagnostics.
 //! - [`ariadne`](https://crates.io/crates/ariadne) for pushing forward how