From 64567c4819ff76cec66a74e87c9e47b1f6f9b609 Mon Sep 17 00:00:00 2001
From: lawrence3699 <lawrence3699@users.noreply.github.com>
Date: Tue, 28 Apr 2026 01:11:06 +1000
Subject: [PATCH] Propagate initial input read errors

---
 CHANGELOG.md    |  1 +
 src/input.rs    | 44 +++++++++++++++++++++++++++++++++++---------
 src/lessopen.rs |  4 ++--
 3 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8eabb7d4..066b1161 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 - Syntax highlighting for Python files using uv as script runner in shebang #3689 (@janlarres)
 
 ## Bugfixes
+- Report initial input read errors instead of treating them as empty input. Closes #3002, see #3706 (@lawrence3699)
 - Treat ZIP archives as binary content based on their magic header, see #3686 (@officialasishkumar)
 - Fix i686 `.deb` package using incorrect architecture name (`i686` instead of `i386`), preventing installation on Debian. Closes #3611, see #3650 (@Sim-hu)
 - Fix inconsistent `.deb` MUSL package names (aarch64-musl used `arm64` instead of `musl-linux-arm64`, and `musleabihf` target missed `bat-musl` prefix). Closes #3482, see #3642 (@mvanhorn)
diff --git a/src/input.rs b/src/input.rs
index 30f13f98..a3420123 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -207,7 +207,7 @@ impl<'a> Input<'a> {
                     kind: OpenedInputKind::StdIn,
                     description,
                     metadata: self.metadata,
-                    reader: InputReader::new(stdin),
+                    reader: InputReader::try_new(stdin)?,
                 })
             }
 
@@ -236,14 +236,14 @@ impl<'a> Input<'a> {
                         file = input_identifier.into_inner().expect("The file was lost in the clircle::Identifier, this should not have happened...");
                     }
 
-                    InputReader::new(BufReader::new(file))
+                    InputReader::try_new(BufReader::new(file))?
                 },
             }),
             InputKind::CustomReader(reader) => Ok(OpenedInput {
                 description,
                 kind: OpenedInputKind::CustomReader,
                 metadata: self.metadata,
-                reader: InputReader::new(BufReader::new(reader)),
+                reader: InputReader::try_new(BufReader::new(reader))?,
             }),
         }
     }
@@ -257,24 +257,29 @@ pub(crate) struct InputReader<'a> {
 }
 
 impl<'a> InputReader<'a> {
-    pub(crate) fn new<R: BufRead + 'a>(mut reader: R) -> InputReader<'a> {
+    #[cfg(test)]
+    pub(crate) fn new<R: BufRead + 'a>(reader: R) -> InputReader<'a> {
+        Self::try_new(reader).expect("reading the first line failed")
+    }
+
+    pub(crate) fn try_new<R: BufRead + 'a>(mut reader: R) -> io::Result<InputReader<'a>> {
         let mut first_line = vec![];
-        reader.read_until(b'\n', &mut first_line).ok();
+        reader.read_until(b'\n', &mut first_line)?;
 
         let content_type = inspect_content_type(&first_line);
 
         if content_type == Some(ContentType::UTF_16LE) {
-            read_utf16_line(&mut reader, &mut first_line, 0x00, 0x0A).ok();
+            read_utf16_line(&mut reader, &mut first_line, 0x00, 0x0A)?;
         } else if content_type == Some(ContentType::UTF_16BE) {
-            read_utf16_line(&mut reader, &mut first_line, 0x0A, 0x00).ok();
+            read_utf16_line(&mut reader, &mut first_line, 0x0A, 0x00)?;
         }
 
-        InputReader {
+        Ok(InputReader {
             inner: Box::new(reader),
             first_line,
             content_type,
             unbuffered: false,
-        }
+        })
     }
 
     pub(crate) fn read_line(&mut self, buf: &mut Vec<u8>) -> io::Result<bool> {
@@ -405,6 +410,27 @@ fn non_zip_pk_prefix_is_not_treated_as_binary() {
     );
 }
 
+#[test]
+fn input_open_returns_initial_read_errors() {
+    struct FailingRead;
+
+    impl Read for FailingRead {
+        fn read(&mut self, _buf: &mut [u8]) -> io::Result<usize> {
+            Err(io::Error::other("initial read failed"))
+        }
+    }
+
+    let input = Input::from_reader(Box::new(FailingRead));
+    let result = input.open(io::empty(), None);
+
+    assert!(result.is_err());
+    assert!(result
+        .err()
+        .unwrap()
+        .to_string()
+        .contains("initial read failed"));
+}
+
 #[test]
 fn utf16le() {
     let content = b"\xFF\xFE\x73\x00\x0A\x00\x64\x00";
diff --git a/src/lessopen.rs b/src/lessopen.rs
index 966bc2c0..116206ba 100644
--- a/src/lessopen.rs
+++ b/src/lessopen.rs
@@ -155,7 +155,7 @@ impl LessOpenPreprocessor {
 
         Ok(OpenedInput {
             kind,
-            reader: InputReader::new(BufReader::new(
+            reader: InputReader::try_new(BufReader::new(
                 if matches!(self.kind, LessOpenKind::TempFile) {
                     let lessopen_string = match String::from_utf8(lessopen_stdout) {
                         Ok(string) => string,
@@ -192,7 +192,7 @@ impl LessOpenPreprocessor {
                             .map(|s| s.replacen("%s", &path_str, 1).replacen("%s", "-", 1)),
                     }
                 },
-            )),
+            ))?,
             metadata: input.metadata,
             description: input.description,
         })