move locus calculation to separate function

codespan-reporting/CHANGELOG.md

@@ -64,6 +64,7 @@ This is because some testing dependencies now require this Rust version.
     ```
 
     </details>
+-   `FileId`s must now implement `Ord` instead of just `PartialEq`.
 
 ## [0.11.1] - 2021-01-18
 

codespan-reporting/examples/custom_files.rs

@@ -74,7 +74,7 @@ mod files {
     }
 
     /// An opaque file identifier.
-    #[derive(Copy, Clone, PartialEq, Eq)]
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
     pub struct FileId(u32);
 
     #[derive(Debug, Clone)]

codespan-reporting/src/diagnostic.rs

@@ -2,6 +2,7 @@
 
 #[cfg(feature = "serialization")]
 use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
 use std::ops::Range;
 use std::string::ToString;
 
@@ -32,7 +33,7 @@ pub enum Severity {
     Bug,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 #[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
 pub enum LabelStyle {
     /// Labels that describe the primary cause of a diagnostic.
@@ -95,7 +96,9 @@ impl<FileId> Label<FileId> {
 /// Represents a diagnostic message that can provide information like errors and
 /// warnings to the user.
 ///
-/// The position of a Diagnostic is considered to be the position of the [`Label`] that has the earliest starting position and has the highest style which appears in all the labels of the diagnostic.
+/// The position of a Diagnostic is considered to be the position of the
+/// [`Label`] that has the earliest starting position and has the highest style
+/// which appears in all the labels of the diagnostic.
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "serialization", derive(Serialize, Deserialize))]
 pub struct Diagnostic<FileId> {
@@ -188,4 +191,36 @@ impl<FileId> Diagnostic<FileId> {
         self.notes.append(&mut notes);
         self
     }
+
+    /// Calculate the locus of this diagnostic.
+    ///
+    /// If this Diagnostic covers multple files, a Vec with multiple values
+    /// will be returned. Or contrary, if there are no labels in the
+    /// Diagnostic, an empty Vec will be returned.
+    pub fn locuses(&self) -> BTreeMap<FileId, usize>
+    where
+        FileId: Copy + Ord,
+    {
+        let mut labels = self
+            .labels
+            .iter()
+            .map(|label| (label.file_id, label.style, label.range.start))
+            .collect::<Vec<_>>();
+
+        labels.sort_unstable_by(|a, b| {
+            a.0.partial_cmp(&b.0)
+                .unwrap_or(std::cmp::Ordering::Equal)
+                .then_with(|| a.1.cmp(&b.1))
+                .then_with(|| a.2.cmp(&b.2))
+                // reverse the sorting so we can use `Extend` to deduplicate
+                .reverse()
+        });
+
+        labels
+            .drain(..)
+            // the label style was only needed for sorting
+            .map(|(file, _, start)| (file, start))
+            // this also deduplicates
+            .collect()
+    }
 }

codespan-reporting/src/files.rs

@@ -85,7 +85,7 @@ impl std::error::Error for Error {
 pub trait Files<'a> {
     /// A unique identifier for files in the file provider. This will be used
     /// for rendering `diagnostic::Label`s in the corresponding source files.
-    type FileId: 'a + Copy + PartialEq;
+    type FileId: 'a + Copy + Ord;
     /// The user-facing name of a file, to be displayed in diagnostics.
     type Name: 'a + std::fmt::Display;
     /// The source code of a file.

codespan-reporting/src/term/views.rs

@@ -21,7 +21,7 @@ pub struct RichDiagnostic<'diagnostic, 'config, FileId> {
 
 impl<'diagnostic, 'config, FileId> RichDiagnostic<'diagnostic, 'config, FileId>
 where
-    FileId: Copy + PartialEq,
+    FileId: Copy + Ord,
 {
     pub fn new(
         diagnostic: &'diagnostic Diagnostic<FileId>,
@@ -42,12 +42,10 @@ where
 
         struct LabeledFile<'diagnostic, FileId> {
             file_id: FileId,
-            start: usize,
             name: String,
             location: Location,
             num_multi_labels: usize,
             lines: BTreeMap<usize, Line<'diagnostic>>,
-            max_label_style: LabelStyle,
         }
 
         impl<'diagnostic, FileId> LabeledFile<'diagnostic, FileId> {
@@ -83,6 +81,8 @@ where
         // snippets of source code.
         let mut outer_padding = 0;
 
+        let locuses = self.diagnostic.locuses();
+
         // Group labels by file
         for label in &self.diagnostic.labels {
             let start_line_index = files.line_index(label.file_id, label.range.start)?;
@@ -102,29 +102,19 @@ where
                 .iter_mut()
                 .find(|labeled_file| label.file_id == labeled_file.file_id)
             {
-                Some(labeled_file) => {
-                    // another diagnostic also referenced this file
-                    if labeled_file.max_label_style > label.style
-                        || (labeled_file.max_label_style == label.style
-                            && labeled_file.start > label.range.start)
-                    {
-                        // this label has a higher style or has the same style but starts earlier
-                        labeled_file.start = label.range.start;
-                        labeled_file.location = files.location(label.file_id, label.range.start)?;
-                        labeled_file.max_label_style = label.style;
-                    }
-                    labeled_file
-                }
+                Some(labeled_file) => labeled_file,
                 None => {
+                    let location = *locuses
+                        .get(&label.file_id)
+                        .expect("file missing from locuses");
+
                     // no other diagnostic referenced this file yet
                     labeled_files.push(LabeledFile {
                         file_id: label.file_id,
-                        start: label.range.start,
                         name: files.name(label.file_id)?.to_string(),
-                        location: files.location(label.file_id, label.range.start)?,
+                        location: files.location(label.file_id, location)?,
                         num_multi_labels: 0,
                         lines: BTreeMap::new(),
-                        max_label_style: label.style,
                     });
                     // this unwrap should never fail because we just pushed an element
                     labeled_files
@@ -441,7 +431,7 @@ pub struct ShortDiagnostic<'diagnostic, FileId> {
 
 impl<'diagnostic, FileId> ShortDiagnostic<'diagnostic, FileId>
 where
-    FileId: Copy + PartialEq,
+    FileId: Copy + Ord,
 {
     pub fn new(
         diagnostic: &'diagnostic Diagnostic<FileId>,