feat: Span visualization command

harper-cli/src/main.rs

@@ -26,6 +26,11 @@ enum Args {
         /// The file you wish to parse.
         file: PathBuf,
     },
+    /// Parse a provided document and show the spans of the detected tokens.
+    Spans {
+        /// The file you wish to display the spans.
+        file: PathBuf,
+    },
     /// Emit decompressed, line-separated list of words in Harper's dictionary.
     Words,
 }
@@ -72,7 +77,7 @@ fn main() -> anyhow::Result<()> {
             let report = report_builder.finish();
             report.print((&filename, Source::from(source)))?;
 
-            std::process::exit(1);
+            Ok(())
         }
         Args::Parse { file } => {
             let (doc, _) = load_file(&file)?;
@@ -84,6 +89,39 @@ fn main() -> anyhow::Result<()> {
 
             Ok(())
         }
+        Args::Spans { file } => {
+            let (doc, source) = load_file(&file)?;
+
+            let primary_color = Color::Blue;
+            let secondary_color = Color::Magenta;
+            let filename = file
+                .file_name()
+                .map(|s| s.to_string_lossy().into())
+                .unwrap_or("<file>".to_string());
+
+            let mut report_builder =
+                Report::build(ReportKind::Custom("Spans", primary_color), &filename, 0);
+            let mut color = primary_color;
+            for token in doc.tokens() {
+                report_builder = report_builder.with_label(
+                    Label::new((&filename, token.span.into()))
+                        .with_message(format!("[{}, {})", token.span.start, token.span.end))
+                        .with_color(color),
+                );
+
+                // Alternate colors so spans are clear
+                color = if color == primary_color {
+                    secondary_color
+                } else {
+                    primary_color
+                };
+            }
+
+            let report = report_builder.finish();
+            report.print((&filename, Source::from(source)))?;
+
+            Ok(())
+        }
         Args::Words => {
             let dict = FstDictionary::curated();
 

justfile

@@ -173,6 +173,10 @@ parse file:
 lint file:
   cargo run --bin harper-cli -- lint {{file}}
 
+# Show the spans of the parsed tokens overlapped on the file.
+spans file:
+  cargo run --bin harper-cli -- spans {{file}}
+
 # Add a noun to Harper's curated dictionary.
 addnoun noun:
   #! /bin/bash