feat(protocol): improvements to snippets API

src/protocol.rs

@@ -4,7 +4,7 @@ that you can implement to get access to miette's (and related library's) full
 reporting and such features.
 */
 
-use std::fmt::Display;
+use std::{fmt::Display, sync::Arc};
 
 use crate::MietteError;
 
@@ -36,14 +36,16 @@ pub trait Diagnostic: std::error::Error {
 
     /// Additional contextual snippets. This is typically used for adding
     /// marked-up source file output the way compilers often do.
-    fn snippets(&self) -> Option<&[DiagnosticSnippet]> {
+    fn snippets(&self) -> Option<Box<dyn Iterator<Item = DiagnosticSnippet>>> {
         None
     }
 }
 
 impl std::error::Error for Box<dyn Diagnostic> {}
 
-impl<T: Diagnostic + Send + Sync + 'static> From<T> for Box<dyn Diagnostic + Send + Sync + 'static> {
+impl<T: Diagnostic + Send + Sync + 'static> From<T>
+    for Box<dyn Diagnostic + Send + Sync + 'static>
+{
     fn from(diag: T) -> Self {
         Box::new(diag)
     }
@@ -112,8 +114,10 @@ support Sources which are gigabytes or larger in size.
 */
 pub trait Source: std::fmt::Debug + Send + Sync + 'static {
     /// Read the bytes for a specific span from this Source.
-    fn read_span<'a>(&'a self, span: &SourceSpan)
-        -> Result<Box<dyn SpanContents + 'a>, MietteError>;
+    fn read_span<'a>(
+        &'a self,
+        span: &SourceSpan,
+    ) -> Result<Box<dyn SpanContents + 'a>, MietteError>;
 }
 
 /**
@@ -166,14 +170,14 @@ impl<'a> SpanContents for MietteSpanContents<'a> {
 /**
 A snippet from a [Source] to be displayed with a message and possibly some highlights.
  */
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct DiagnosticSnippet {
     /// Explanation of this specific diagnostic snippet.
     pub message: Option<String>,
     /// The "filename" for this snippet.
     pub source_name: String,
     /// A [Source] that can be used to read the actual text of a source.
-    pub source: Box<dyn Source>,
+    pub source: Arc<dyn Source>,
     /// The primary [SourceSpan] where this diagnostic is located.
     pub context: SourceSpan,
     /// Additional [SourceSpan]s that mark specific sections of the span, for

src/reporter.rs

@@ -7,7 +7,7 @@ use std::fmt;
 use indenter::indented;
 
 use crate::chain::Chain;
-use crate::protocol::{Diagnostic, DiagnosticSnippet, DiagnosticReporter, Severity};
+use crate::protocol::{Diagnostic, DiagnosticReporter, DiagnosticSnippet, Severity};
 
 /**
 Reference implementation of the [DiagnosticReporter] trait. This is generally
@@ -17,7 +17,11 @@ you want custom reporting for your tool or app.
 pub struct MietteReporter;
 
 impl MietteReporter {
-    fn render_snippet(&self, f: &mut fmt::Formatter<'_>, snippet: &DiagnosticSnippet) -> fmt::Result {
+    fn render_snippet(
+        &self,
+        f: &mut fmt::Formatter<'_>,
+        snippet: &DiagnosticSnippet,
+    ) -> fmt::Result {
         use fmt::Write as _;
         write!(f, "\n[{}]", snippet.source_name)?;
         if let Some(msg) = &snippet.message {
@@ -126,7 +130,7 @@ impl DiagnosticReporter for MietteReporter {
         if let Some(snippets) = diagnostic.snippets() {
             writeln!(f)?;
             for snippet in snippets {
-                self.render_snippet(f, snippet)?;
+                self.render_snippet(f, &snippet)?;
             }
         }
 
@@ -166,7 +170,7 @@ impl DiagnosticReporter for JokeReporter {
             "miette, her eyes enormous: you {} miette? you {}? oh! oh! jail for mother! jail for mother for One Thousand Years!!!!",
             diagnostic.code(),
             diagnostic.snippets().map(|snippets| {
-                snippets.iter().map(|snippet| snippet.message.clone()).collect::<Option<Vec<String>>>()
+                snippets.map(|snippet| snippet.message).collect::<Option<Vec<String>>>()
             }).flatten().map(|x| x.join(", ")).unwrap_or_else(||"try and cause miette to panic".into())
         )?;
 

tests/reporter.rs

@@ -27,8 +27,8 @@ impl Diagnostic for MyBad {
         Some(&"try doing it better next time?")
     }
 
-    fn snippets(&self) -> Option<&[DiagnosticSnippet]> {
-        Some(&self.snippets)
+    fn snippets(&self) -> Option<Box<dyn Iterator<Item = DiagnosticSnippet>>> {
+        Some(Box::new(self.snippets.clone().into_iter()))
     }
 }
 
@@ -48,20 +48,22 @@ fn basic() -> Result<(), MietteError> {
 #[test]
 fn fancy() -> Result<(), MietteError> {
     let src = "source\n  text\n    here".to_string();
+    let len = src.len();
     let err = MyBad {
         snippets: vec![DiagnosticSnippet {
             message: Some("This is the part that broke".into()),
             source_name: "bad_file.rs".into(),
-            source: Box::new(src.clone()),
-            highlights: Some(vec![
-                ("this bit here".into(), SourceSpan {
+            source: Arc::new(src),
+            highlights: Some(vec![(
+                "this bit here".into(),
+                SourceSpan {
                     start: 9.into(),
                     end: 12.into(),
-                })
-            ]),
+                },
+            )]),
             context: SourceSpan {
                 start: 0.into(),
-                end: (src.len() - 1).into(),
+                end: (len - 1).into(),
             },
         }],
     };