comparison rust/hg-core/src/revlog/mod.rs @ 50744:bca4037306da stable

rust-revlog: fix incorrect results with NULL_NODE prefixes

In case a short hash is a prefix of `NULL_NODE`, the correct revision
number lookup is `NULL_REVISION` only if there is no match in the nodemap.
Indeed, if there is a single nodemap match, then it is an ambiguity with the
always matching `NULL_NODE`.

Before this change, using the Mercurial development repository as a testbed (it
has public changesets with node ID starting with `0005` and `0009`), this is
what `rhg` did (plain `hg` provided for reference)

```
$ rust/target/debug/rhg cat -r 000 README
README: no such file in rev 000000000000
$ hg cat -r 000 README
abort: ambiguous revision identifier: 000
```

Here is the expected output for `rhg` on ambiguous prefixes (again, before
this change):

```
$ rust/target/debug/rhg cat -r 0001 README
abort: ambiguous revision identifier: 0001
```

The test provided by 8c29af0f6d6e in `test-rhg.t` could become flaky with
this change, unless all hashes are fixed. We expect reviewers to be more
sure about that than we are.

50743:0159b014f3ab

    /// revlog
    pub fn rev_from_node(
        &self,
        node: NodePrefix,
    ) -> Result<Revision, RevlogError> {
        if node.is_prefix_of(&NULL_NODE) {
            return Ok(NULL_REVISION);
        }

        if let Some(nodemap) = &self.nodemap {
            return nodemap
                .find_bin(&self.index, node)?
                .ok_or(RevlogError::InvalidRevision);
        }
        self.rev_from_node_no_persistent_nodemap(node)
    }

    /// Same as `rev_from_node`, without using a persistent nodemap
    ///
    /// This is used as fallback when a persistent nodemap is not present.

        let revlog = Revlog::open(&vfs, "foo.i", None, false).unwrap();
        assert!(revlog.is_empty());
        assert_eq!(revlog.len(), 0);
        assert!(revlog.get_entry(0).is_err());
        assert!(!revlog.has_rev(0));
    }

    #[test]
    fn test_inline() {
        let temp = tempfile::tempdir().unwrap();

        assert_eq!(p1_entry.unwrap().revision(), 0);
        let p2_entry = entry2.p2_entry().unwrap();
        assert!(p2_entry.is_some());
        assert_eq!(p2_entry.unwrap().revision(), 1);
    }
}

50744:bca4037306da

    /// revlog
    pub fn rev_from_node(
        &self,
        node: NodePrefix,
    ) -> Result<Revision, RevlogError> {
        let looked_up = if let Some(nodemap) = &self.nodemap {
            nodemap
                .find_bin(&self.index, node)?
                .ok_or(RevlogError::InvalidRevision)
        } else {
            self.rev_from_node_no_persistent_nodemap(node)
        };

        if node.is_prefix_of(&NULL_NODE) {
            return match looked_up {
                Ok(_) => Err(RevlogError::AmbiguousPrefix),
                Err(RevlogError::InvalidRevision) => Ok(NULL_REVISION),
                res => res,
            };
        };

        looked_up
    }

    /// Same as `rev_from_node`, without using a persistent nodemap
    ///
    /// This is used as fallback when a persistent nodemap is not present.

        let revlog = Revlog::open(&vfs, "foo.i", None, false).unwrap();
        assert!(revlog.is_empty());
        assert_eq!(revlog.len(), 0);
        assert!(revlog.get_entry(0).is_err());
        assert!(!revlog.has_rev(0));
        assert_eq!(revlog.rev_from_node(NULL_NODE.into()).unwrap(), -1);
    }

    #[test]
    fn test_inline() {
        let temp = tempfile::tempdir().unwrap();

        assert_eq!(p1_entry.unwrap().revision(), 0);
        let p2_entry = entry2.p2_entry().unwrap();
        assert!(p2_entry.is_some());
        assert_eq!(p2_entry.unwrap().revision(), 1);
    }

    #[test]
    fn test_nodemap() {
        let temp = tempfile::tempdir().unwrap();
        let vfs = Vfs { base: temp.path() };

        // building a revlog with a forced Node starting with zeros
        // This is a corruption, but it does not preclude using the nodemap
        // if we don't try and access the data
        let node0 = Node::from_hex("00d2a3912a0b24502043eae84ee4b279c18b90dd")
            .unwrap();
        let node1 = Node::from_hex("b004912a8510032a0350a74daa2803dadfb00e12")
            .unwrap();
        let entry0_bytes = IndexEntryBuilder::new()
            .is_first(true)
            .with_version(1)
            .with_inline(true)
            .with_offset(INDEX_ENTRY_SIZE)
            .with_node(node0)
            .build();
        let entry1_bytes = IndexEntryBuilder::new()
            .with_offset(INDEX_ENTRY_SIZE)
            .with_node(node1)
            .build();
        let contents = vec![entry0_bytes, entry1_bytes]
            .into_iter()
            .flatten()
            .collect_vec();
        std::fs::write(temp.path().join("foo.i"), contents).unwrap();
        let revlog = Revlog::open(&vfs, "foo.i", None, false).unwrap();

        // accessing the data shows the corruption
        revlog.get_entry(0).unwrap().data().unwrap_err();

        assert_eq!(revlog.rev_from_node(NULL_NODE.into()).unwrap(), -1);
        assert_eq!(revlog.rev_from_node(node0.into()).unwrap(), 0);
        assert_eq!(revlog.rev_from_node(node1.into()).unwrap(), 1);
        assert_eq!(
            revlog
                .rev_from_node(NodePrefix::from_hex("000").unwrap())
                .unwrap(),
            -1
        );
        assert_eq!(
            revlog
                .rev_from_node(NodePrefix::from_hex("b00").unwrap())
                .unwrap(),
            1
        );
        // RevlogError does not implement PartialEq
        // (ultimately because io::Error does not)
        match revlog
            .rev_from_node(NodePrefix::from_hex("00").unwrap())
            .expect_err("Expected to give AmbiguousPrefix error")
        {
            RevlogError::AmbiguousPrefix => (),
            e => {
                panic!("Got another error than AmbiguousPrefix: {:?}", e);
            }
        };
    }
}