Allow miette users to opt-out of the rendering of the cause chain

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 {
@@ -86,6 +87,18 @@ impl MietteHandlerOpts {
         self.width = Some(width);
         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 
         }
     }
 
@@ -78,6 +81,18 @@ 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.
     ///
@@ -134,7 +149,9 @@ impl GraphicalReportHandler {
     ) -> fmt::Result {
         self.render_header(f, diagnostic)?;
         writeln!(f)?;
-        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/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>,
 }
 
@@ -24,8 +25,21 @@ 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 {
@@ -57,7 +71,9 @@ 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)?;