fix: restore verbose error reporting capabilities when parsing of objects fails.

When `verbose-object-parsing-errors` is enabled, it will now once again
provide greater details as to where and why the parsing failed.

Author: Byron

gix-object/Cargo.toml

@@ -25,7 +25,7 @@ serde = ["dep:serde", "bstr/serde", "smallvec/serde", "gix-hash/serde", "gix-act
 ## details information about the error location will be collected.
 ## Use it in applications which expect broken or invalid objects or for debugging purposes. Incorrectly formatted objects aren't at all
 ## common otherwise.
-verbose-object-parsing-errors = []
+verbose-object-parsing-errors = ["winnow/std"]
 
 [dependencies]
 gix-features = { version = "^0.36.0", path = "../gix-features", features = ["rustsha1", "progress"] }

gix-object/src/lib.rs

@@ -290,6 +290,12 @@ pub mod decode {
                 self.inner.fmt(f)
             }
         }
+
+        impl std::error::Error for Error {
+            fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+                self.inner.cause().map(|v| v as &(dyn std::error::Error + 'static))
+            }
+        }
     }
 
     ///
@@ -318,14 +324,15 @@ pub mod decode {
         }
 
         impl std::fmt::Display for Error {
-            fn fmt(&self, _f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                Ok(())
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                f.write_str("object parsing failed")
             }
         }
+
+        impl std::error::Error for Error {}
     }
     pub(crate) use _decode::empty_error;
     pub use _decode::{Error, ParseError};
-    impl std::error::Error for Error {}
 
     /// Returned by [`loose_header()`]
     #[derive(Debug, thiserror::Error)]

gix-object/src/tree/ref_iter.rs

@@ -67,11 +67,11 @@ impl<'a> Iterator for TreeRefIter<'a> {
                 Some(Ok(entry))
             }
             None => {
+                let failing = self.data;
                 self.data = &[];
-                let empty = &[] as &[u8];
                 #[allow(clippy::unit_arg)]
                 Some(Err(crate::decode::Error::with_err(
-                    winnow::error::ErrMode::from_error_kind(&empty, winnow::error::ErrorKind::Verify),
+                    winnow::error::ErrMode::from_error_kind(&failing, winnow::error::ErrorKind::Verify),
                 )))
             }
         }

gix-object/tests/commit/mod.rs

@@ -1,3 +1,6 @@
+use crate::fixture_name;
+use gix_object::{CommitRef, CommitRefIter};
+
 const SIGNATURE: & [u8; 487] = b"-----BEGIN PGP SIGNATURE-----\n\niQEzBAABCAAdFiEEdjYp/sh4j8NRKLX27gKdHl60AwAFAl7q2DsACgkQ7gKdHl60\nAwDvewgAkL5UjEztzeVXlzceom0uCrAkCw9wSGLTmYcMKW3JwEaTRgQ4FX+sDuFT\nLZ8DoPu3UHUP0QnKrUwHulTTlKcOAvsczHbVPIKtXCxo6QpUfhsJQwz/J29kiE4L\nsOd+lqKGnn4oati/de2xwqNGi081fO5KILX75z6KfsAe7Qz7R3jxRF4uzHI033O+\nJc2Y827XeaELxW40SmzoLanWgEcdreXf3PstXEWW77CAu0ozXmvYj56vTviVybxx\nG7bc8lwc+SSKVe2VVB+CCfVbs0i541gmghUpZfMhUgaqttcCH8ysrUJDhne1BLG8\nCrOJIWTwAeEDtomV1p76qrMeqr1GFg==\n=qlSN\n-----END PGP SIGNATURE-----";
 
 const LONG_MESSAGE: &str = "Merge tag 'thermal-v5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thermal/linux
@@ -159,6 +162,27 @@ mod method {
     }
 }
 
+#[test]
+fn invalid() {
+    let fixture = fixture_name("commit", "unsigned.txt");
+    let partial_commit = &fixture[..fixture.len() / 2];
+    assert_eq!(
+        CommitRef::from_bytes(partial_commit).unwrap_err().to_string(),
+        if cfg!(feature = "verbose-object-parsing-errors") {
+            "expected `<timestamp>`, `<name> <<email>> <timestamp> <+|-><HHMM>`, `author <signature>`"
+        } else {
+            "object parsing failed"
+        }
+    );
+    assert_eq!(
+        CommitRefIter::from_bytes(partial_commit)
+            .take_while(Result::is_ok)
+            .count(),
+        1,
+        "we can decode some fields before failing"
+    );
+}
+
 mod from_bytes;
 mod iter;
 mod message;

gix-object/tests/tag/mod.rs

@@ -1,5 +1,6 @@
+use crate::fixture_name;
 use gix_date::time::Sign;
-use gix_object::{bstr::ByteSlice, Kind, TagRef};
+use gix_object::{bstr::ByteSlice, Kind, TagRef, TagRefIter};
 
 mod method {
     use gix_object::TagRef;
@@ -115,6 +116,25 @@ KLMHist5yj0sw1E4hDTyQa0=
     }
 }
 
+#[test]
+fn invalid() {
+    let fixture = fixture_name("tag", "whitespace.txt");
+    let partial_tag = &fixture[..fixture.len() / 2];
+    assert_eq!(
+        TagRef::from_bytes(partial_tag).unwrap_err().to_string(),
+        if cfg!(feature = "verbose-object-parsing-errors") {
+            ""
+        } else {
+            "object parsing failed"
+        }
+    );
+    assert_eq!(
+        TagRefIter::from_bytes(partial_tag).take_while(Result::is_ok).count(),
+        4,
+        "we can decode some fields before failing"
+    );
+}
+
 mod from_bytes {
     use gix_object::{bstr::ByteSlice, Kind, TagRef};
 

gix-object/tests/tree/mod.rs

@@ -107,6 +107,25 @@ mod from_bytes {
         Ok(())
     }
 
+    #[test]
+    fn invalid() {
+        let fixture = fixture_name("tree", "definitely-special.tree");
+        let partial_tree = &fixture[..fixture.len() / 2];
+        assert_eq!(
+            TreeRef::from_bytes(partial_tree).unwrap_err().to_string(),
+            if cfg!(feature = "verbose-object-parsing-errors") {
+                ""
+            } else {
+                "object parsing failed"
+            }
+        );
+        assert_eq!(
+            TreeRefIter::from_bytes(partial_tree).take_while(Result::is_ok).count(),
+            9,
+            "we can decode about half of it before failing"
+        );
+    }
+
     #[test]
     fn special_trees() -> crate::Result {
         for (name, expected_entry_count) in [