fix(read): fallback to raw bytes for non-UTF-8 reads

src/cmds/system/read.rs

@@ -4,6 +4,7 @@ use crate::core::filter::{self, FilterLevel, Language};
 use crate::core::tracking;
 use anyhow::{Context, Result};
 use std::fs;
+use std::io::Write;
 use std::path::Path;
 
 pub fn run(
@@ -20,9 +21,28 @@ pub fn run(
         eprintln!("Reading: {} (filter: {})", file.display(), level);
     }
 
-    // Read file content
-    let content = fs::read_to_string(file)
-        .with_context(|| format!("Failed to read file: {}", file.display()))?;
+    let bytes = fs::read(file).with_context(|| format!("Failed to read file: {}", file.display()))?;
+    let content = match String::from_utf8(bytes.clone()) {
+        Ok(content) => content,
+        Err(_) if supports_binary_passthrough(level, max_lines, tail_lines, line_numbers) => {
+            if verbose > 0 {
+                eprintln!(
+                    "rtk: warning: {} is non-UTF-8, using raw byte passthrough",
+                    file.display()
+                );
+            }
+            let mut stdout = std::io::stdout().lock();
+            stdout.write_all(&bytes)?;
+            timer.track_passthrough(&format!("cat {}", file.display()), "rtk read");
+            return Ok(());
+        }
+        Err(_) => {
+            anyhow::bail!(
+                "Failed to read file: {}: stream did not contain valid UTF-8",
+                file.display()
+            );
+        }
+    };
 
     // Detect language from extension
     let lang = file
@@ -176,6 +196,18 @@ fn apply_line_window(
     content.to_string()
 }
 
+fn supports_binary_passthrough(
+    level: FilterLevel,
+    max_lines: Option<usize>,
+    tail_lines: Option<usize>,
+    line_numbers: bool,
+) -> bool {
+    level == FilterLevel::None
+        && max_lines.is_none()
+        && tail_lines.is_none()
+        && !line_numbers
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -227,6 +259,40 @@ fn main() {{
         assert!(output.contains("more lines"));
     }
 
+    #[test]
+    fn test_supports_binary_passthrough_only_for_plain_reads() {
+        assert!(supports_binary_passthrough(
+            FilterLevel::None,
+            None,
+            None,
+            false
+        ));
+        assert!(!supports_binary_passthrough(
+            FilterLevel::Minimal,
+            None,
+            None,
+            false
+        ));
+        assert!(!supports_binary_passthrough(
+            FilterLevel::None,
+            Some(10),
+            None,
+            false
+        ));
+        assert!(!supports_binary_passthrough(
+            FilterLevel::None,
+            None,
+            Some(10),
+            false
+        ));
+        assert!(!supports_binary_passthrough(
+            FilterLevel::None,
+            None,
+            None,
+            true
+        ));
+    }
+
     fn rtk_bin() -> std::path::PathBuf {
         std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
             .join("target")