Report implement Error, and a few more suggestions

examples/multifile.rs

@@ -25,10 +25,10 @@ fn main() {
             .with_message(format!("Original definition of {} is here", "five".fg(a)))
             .with_color(a))
         .with_note(format!("{} is a number and can only be added to other numbers", "Nat".fg(a)))
-        .finish()
-        .print(sources(vec![
+        .finish(sources(vec![
             ("a.tao", include_str!("a.tao")),
             ("b.tao", include_str!("b.tao")),
         ]))
+        .print()
         .unwrap();
 }

examples/multiline.rs

@@ -37,7 +37,7 @@ fn main() {
             ))
             .with_color(out2))
         .with_note(format!("Outputs of {} expressions must coerce to the same type", "match".fg(out)))
-        .finish()
-        .print(("sample.tao", Source::from(include_str!("sample.tao"))))
+        .finish(("sample.tao", Source::from(include_str!("sample.tao"))))
+        .print()
         .unwrap();
 }

examples/simple.rs

@@ -6,8 +6,8 @@ fn main() {
         .with_message("Incompatible types")
         .with_label(Label::new(32..33).with_message("This is of type Nat"))
         .with_label(Label::new(42..45).with_message("This is of type Str"))
-        .finish()
-        .print(Source::from(include_str!("sample.tao")))
+        .finish(Source::from(include_str!("sample.tao")))
+        .print()
         .unwrap();
 
     const SOURCE: &str = "a b c d e f";
@@ -19,7 +19,7 @@ fn main() {
         .with_label(Label::new(2..3).with_color(Color::Blue).with_message("`b` for banana").with_order(1))
         .with_label(Label::new(4..5).with_color(Color::Green))
         .with_label(Label::new(7..9).with_color(Color::Cyan).with_message("`e` for emerald"))
-        .finish()
-        .print(Source::from(SOURCE))
+        .finish(Source::from(SOURCE))
+        .print()
         .unwrap();
 }

examples/stresstest.rs

@@ -53,7 +53,7 @@ fn main() {
             .with_compact(true)
             .with_underlines(true)
             .with_tab_width(4))
-        .finish()
-        .print(("stresstest.tao", Source::from(include_str!("stresstest.tao"))))
+        .finish(("stresstest.tao", Source::from(include_str!("stresstest.tao"))))
+        .print()
         .unwrap();
 }

src/lib.rs

@@ -23,6 +23,7 @@ use std::{
     cmp::{PartialEq, Eq},
     fmt,
 };
+use std::fmt::Formatter;
 use unicode_width::UnicodeWidthChar;
 
 /// A trait implemented by spans within a character-based source.
@@ -152,6 +153,7 @@ pub struct Report<'a, S: Span = Range<usize>> {
     location: (<S::SourceId as ToOwned>::Owned, usize),
     labels: Vec<Label<S>>,
     config: Config,
+    rendered: Option<String>
 }
 
 impl<S: Span> Report<'_, S> {
@@ -170,16 +172,23 @@ impl<S: Span> Report<'_, S> {
     }
 
     /// Write this diagnostic out to `stderr`.
-    pub fn eprint<C: Cache<S::SourceId>>(&self, cache: C) -> io::Result<()> {
-        self.write(cache, io::stderr())
+    pub fn eprint(&self) -> io::Result<()> {
+        write!(io::stderr(), "{}", self.rendered.as_ref().unwrap())
     }
 
     /// Write this diagnostic out to `stdout`.
     ///
     /// In most cases, [`Report::eprint`] is the
     /// ['more correct'](https://en.wikipedia.org/wiki/Standard_streams#Standard_error_(stderr)) function to use.
-    pub fn print<C: Cache<S::SourceId>>(&self, cache: C) -> io::Result<()> {
-        self.write_for_stdout(cache, io::stdout())
+    pub fn print(&self) -> io::Result<()> {
+        write!(io::stdout(), "{}", self.rendered.as_ref().unwrap())
+    }
+
+    /// TODO: Move the description from the fork
+    fn write_to_string<C: Cache<S::SourceId>>(&self, cache: C) -> String {
+        let mut vec = Vec::new();
+        self.write(cache, &mut vec).unwrap();
+        String::from_utf8(vec).unwrap()
     }
 }
 
@@ -195,6 +204,21 @@ impl<'a, S: Span> fmt::Debug for Report<'a, S> {
             .finish()
     }
 }
+
+impl<'a, S: Span> fmt::Display for Report<'a, S> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        assert!(
+            self.rendered.is_some(),
+            "A report render is necessary to do display"
+        );
+
+        write!(f, "{}", self.rendered.as_ref().unwrap())
+    }
+}
+
+impl<'a, S: Span> std::error::Error for Report<'a, S> {}
+
+
 /// A type that defines the kind of report being produced.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum ReportKind<'a> {
@@ -303,8 +327,8 @@ impl<'a, S: Span> ReportBuilder<'a, S> {
     }
 
     /// Finish building the [`Report`].
-    pub fn finish(self) -> Report<'a, S> {
-        Report {
+    pub fn finish<C: Cache<S::SourceId>>(self, cache: C) -> Report<'a, S> {
+        let mut report = Report {
             kind: self.kind,
             code: self.code,
             msg: self.msg,
@@ -313,7 +337,11 @@ impl<'a, S: Span> ReportBuilder<'a, S> {
             location: self.location,
             labels: self.labels,
             config: self.config,
-        }
+            rendered: None
+        };
+        report.rendered = Some(report.write_to_string(cache));
+
+        report
     }
 }
 

src/write.rs

@@ -805,15 +805,7 @@ mod tests {
 
     use insta::assert_snapshot;
 
-    use crate::{Cache, CharSet, Config, Label, Report, ReportKind, Source, Span};
-
-    impl<S: Span> Report<'_, S> {
-        fn write_to_string<C: Cache<S::SourceId>>(&self, cache: C) -> String {
-            let mut vec = Vec::new();
-            self.write(cache, &mut vec).unwrap();
-            String::from_utf8(vec).unwrap()
-        }
-    }
+    use crate::{CharSet, Config, Label, Report, ReportKind, Source};
 
     fn no_color_and_ascii() -> Config {
         Config::default()
@@ -828,8 +820,8 @@ mod tests {
         let msg = Report::<Range<usize>>::build(ReportKind::Error, (), 0)
             .with_config(no_color_and_ascii())
             .with_message("can't compare apples with oranges")
-            .finish()
-            .write_to_string(Source::from(""));
+            .finish(Source::from(""))
+            .to_string();
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
         "###)
@@ -843,8 +835,8 @@ mod tests {
             .with_message("can't compare apples with oranges")
             .with_label(Label::new(0..5))
             .with_label(Label::new(9..15))
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         // TODO: it would be nice if these spans still showed up (like codespan-reporting does)
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
@@ -863,8 +855,8 @@ mod tests {
             .with_message("can't compare apples with oranges")
             .with_label(Label::new(0..5).with_message("This is an apple"))
             .with_label(Label::new(9..15).with_message("This is an orange"))
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         // TODO: it would be nice if these lines didn't cross
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
@@ -888,8 +880,8 @@ mod tests {
             .with_label(
                 Label::new(source.len() - 5..source.len()).with_message("This is an orange"),
             )
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         // TODO: it would be nice if the start of long lines would be omitted (like rustc does)
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
@@ -908,8 +900,8 @@ mod tests {
         let msg = Report::<Range<usize>>::build(ReportKind::Error, (), 0)
             .with_config(no_color_and_ascii())
             .with_label(Label::new(0..source.len()).with_message("illegal comparison"))
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         // TODO: it would be nice if the 2nd line wasn't omitted
         assert_snapshot!(msg, @r###"
         Error: 
@@ -931,8 +923,8 @@ mod tests {
             .with_config(no_color_and_ascii())
             .with_label(Label::new(0..source.len()).with_message("URL"))
             .with_label(Label::new(0..source.find(':').unwrap()).with_message("scheme"))
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         // TODO: it would be nice if you could tell where the spans start and end.
         assert_snapshot!(msg, @r###"
         Error: 
@@ -959,8 +951,8 @@ mod tests {
             .with_label(Label::new(9..15).with_message("This is an orange"))
             .with_label(Label::new(9..15).with_message("Have I mentioned that this is an orange?"))
             .with_label(Label::new(9..15).with_message("No really, have I mentioned that?"))
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
            ,-[<unknown>:1:1]
@@ -991,8 +983,8 @@ mod tests {
             .with_label(Label::new(0..5).with_message("This is an apple"))
             .with_label(Label::new(9..15).with_message("This is an orange"))
             .with_note("stop trying ... this is a fruitless endeavor")
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
            ,-[<unknown>:1:1]
@@ -1017,8 +1009,8 @@ mod tests {
             .with_label(Label::new(0..5).with_message("This is an apple"))
             .with_label(Label::new(9..15).with_message("This is an orange"))
             .with_help("have you tried peeling the orange?")
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
            ,-[<unknown>:1:1]
@@ -1044,8 +1036,8 @@ mod tests {
             .with_label(Label::new(9..15).with_message("This is an orange"))
             .with_help("have you tried peeling the orange?")
             .with_note("stop trying ... this is a fruitless endeavor")
-            .finish()
-            .write_to_string(Source::from(source));
+            .finish(Source::from(source))
+            .to_string();
         assert_snapshot!(msg, @r###"
         Error: can't compare apples with oranges
            ,-[<unknown>:1:1]
@@ -1062,4 +1054,22 @@ mod tests {
         ---'
         "###)
     }
+
+    #[test]
+    fn report_to_error() {
+        let source = "apple == orange;";
+        let msg = Report::<Range<usize>>::build(ReportKind::Error, (), 0)
+            .with_config(no_color_and_ascii())
+            .with_message("can't compare apples with oranges")
+            .with_label(Label::new(0..5).with_message("This is an apple"))
+            .with_label(Label::new(9..15).with_message("This is an orange"))
+            .with_help("have you tried peeling the orange?")
+            .with_note("stop trying ... this is a fruitless endeavor")
+            .finish(Source::from(source));
+
+        let err: &dyn std::error::Error = &msg; // This bit compiling proves it is Error
+
+        println!("{err}");
+        println!("{err:?}");
+    }
 }