[WIP] Hide empty snippets for full-file diagnostics

Summary
--

This isn't really polished for review yet, but this is the other commit I wanted
to spin off from #19415.

This suppresses empty snippets for empty ranges at the very beginning of a
file, and for empty ranges in non-existent files. Ruff includes empty ranges for
IO errors, for example.

Test Plan
--

TODO add a `ruff_db` test with an example

Author: ntBre

crates/ruff_annotate_snippets/src/renderer/display_list.rs

@@ -1164,6 +1164,16 @@ fn format_snippet<'m>(
     let main_range = snippet.annotations.first().map(|x| x.range.start);
     let origin = snippet.origin;
     let need_empty_header = origin.is_some() || is_first;
+
+    let is_file_level = snippet.annotations.iter().any(|ann| ann.is_file_level);
+    if is_file_level {
+        let header = format_header(origin, main_range, &[], is_first);
+        return DisplaySet {
+            display_lines: header.map_or_else(Vec::new, |header| vec![header]),
+            margin: Margin::new(0, 0, 0, 0, term_width, 0),
+        };
+    }
+
     let mut body = format_body(
         snippet,
         need_empty_header,

crates/ruff_annotate_snippets/src/snippet.rs

@@ -114,13 +114,19 @@ pub struct Annotation<'a> {
     pub(crate) range: Range<usize>,
     pub(crate) label: Option<&'a str>,
     pub(crate) level: Level,
+    pub(crate) is_file_level: bool,
 }
 
 impl<'a> Annotation<'a> {
     pub fn label(mut self, label: &'a str) -> Self {
         self.label = Some(label);
         self
     }
+
+    pub fn is_file_level(mut self, yes: bool) -> Self {
+        self.is_file_level = yes;
+        self
+    }
 }
 
 /// Types of annotations.
@@ -154,6 +160,7 @@ impl Level {
             range: span,
             label: None,
             level: self,
+            is_file_level: false,
         }
     }
 }

crates/ruff_db/src/diagnostic/mod.rs

@@ -702,6 +702,11 @@ pub struct Annotation {
     is_primary: bool,
     /// The diagnostic tags associated with this annotation.
     tags: Vec<DiagnosticTag>,
+    /// Whether this annotation is a file-level or full-file annotation.
+    ///
+    /// When set, rendering will not include a file snippet but will still have the file's name and
+    /// (optional) range.
+    is_file_level: bool,
 }
 
 impl Annotation {
@@ -720,6 +725,7 @@ impl Annotation {
             message: None,
             is_primary: true,
             tags: Vec::new(),
+            is_file_level: false,
         }
     }
 
@@ -736,6 +742,7 @@ impl Annotation {
             message: None,
             is_primary: false,
             tags: Vec::new(),
+            is_file_level: false,
         }
     }
 
@@ -801,6 +808,10 @@ impl Annotation {
     pub fn push_tag(&mut self, tag: DiagnosticTag) {
         self.tags.push(tag);
     }
+
+    pub fn set_file_level(&mut self, yes: bool) {
+        self.is_file_level = yes;
+    }
 }
 
 /// Tags that can be associated with an annotation.

crates/ruff_db/src/diagnostic/render.rs

@@ -389,6 +389,7 @@ struct ResolvedAnnotation<'a> {
     line_end: OneIndexed,
     message: Option<&'a str>,
     is_primary: bool,
+    is_file_level: bool,
 }
 
 impl<'a> ResolvedAnnotation<'a> {
@@ -434,6 +435,7 @@ impl<'a> ResolvedAnnotation<'a> {
             line_end,
             message: ann.get_message(),
             is_primary: ann.is_primary,
+            is_file_level: ann.is_file_level,
         })
     }
 }
@@ -651,6 +653,8 @@ struct RenderableAnnotation<'r> {
     message: Option<&'r str>,
     /// Whether this annotation is considered "primary" or not.
     is_primary: bool,
+    /// Whether this annotation applies to an entire file, rather than a snippet within it.
+    is_file_level: bool,
 }
 
 impl<'r> RenderableAnnotation<'r> {
@@ -668,6 +672,7 @@ impl<'r> RenderableAnnotation<'r> {
             range,
             message: ann.message,
             is_primary: ann.is_primary,
+            is_file_level: ann.is_file_level,
         }
     }
 
@@ -693,7 +698,7 @@ impl<'r> RenderableAnnotation<'r> {
         if let Some(message) = self.message {
             ann = ann.label(message);
         }
-        ann
+        ann.is_file_level(self.is_file_level)
     }
 }
 

crates/ruff_linter/src/message/mod.rs

@@ -48,8 +48,14 @@ pub fn create_syntax_error_diagnostic(
         Severity::Error,
         format_args!("SyntaxError: {message}"),
     );
-    let span = span.into().with_range(range.range());
-    diag.annotate(Annotation::primary(span));
+    let range = range.range();
+    let span = span.into().with_range(range);
+    let mut annotation = Annotation::primary(span);
+    // The `0..0` range is used to highlight file-level diagnostics.
+    if range == TextRange::default() {
+        annotation.set_file_level(true);
+    }
+    diag.annotate(annotation);
     diag
 }
 
@@ -75,7 +81,11 @@ where
     );
 
     let span = Span::from(file).with_range(range);
-    let annotation = Annotation::primary(span);
+    let mut annotation = Annotation::primary(span);
+    // The `0..0` range is used to highlight file-level diagnostics.
+    if range == TextRange::default() {
+        annotation.set_file_level(true);
+    }
     diagnostic.annotate(annotation);
 
     if let Some(suggestion) = suggestion {