fix!: make V1 shallow announcements possible (#1604)

Author: Byron

gix-protocol/src/fetch/response/mod.rs

@@ -203,6 +203,15 @@ impl Response {
         &self.shallows
     }
 
+    /// Append the given `updates` which may have been obtained from a
+    /// (handshake::Outcome)[crate::handshake::Outcome::v1_shallow_updates].
+    ///
+    /// In V2, these are received as part of the pack, but V1 sends them early, so we
+    /// offer to re-integrate them here.
+    pub fn append_v1_shallow_updates(&mut self, updates: Option<Vec<ShallowUpdate>>) {
+        self.shallows.extend(updates.into_iter().flatten());
+    }
+
     /// Return all wanted-refs [parsed previously][Response::from_line_reader()].
     pub fn wanted_refs(&self) -> &[WantedRef] {
         &self.wanted_refs

gix-protocol/src/fetch_fn.rs

@@ -71,6 +71,7 @@ where
     let crate::handshake::Outcome {
         server_protocol_version: protocol_version,
         refs,
+        v1_shallow_updates: _ignored_shallow_updates_as_it_is_deprecated,
         capabilities,
     } = crate::fetch::handshake(
         &mut transport,

gix-protocol/src/handshake/function.rs

@@ -95,9 +95,14 @@ where
         (actual_protocol, parsed_refs, capabilities)
     }; // this scope is needed, see https://github.com/rust-lang/rust/issues/76149
 
+    let (refs, v1_shallow_updates) = refs
+        .map(|(refs, shallow)| (Some(refs), Some(shallow)))
+        .unwrap_or_default();
+
     Ok(Outcome {
         server_protocol_version,
         refs,
+        v1_shallow_updates,
         capabilities,
     })
 }

gix-protocol/src/handshake/mod.rs

@@ -54,8 +54,11 @@ pub enum Ref {
 pub struct Outcome {
     /// The protocol version the server responded with. It might have downgraded the desired version.
     pub server_protocol_version: gix_transport::Protocol,
-    /// The references reported as part of the Protocol::V1 handshake, or `None` otherwise as V2 requires a separate request.
+    /// The references reported as part of the `Protocol::V1` handshake, or `None` otherwise as V2 requires a separate request.
     pub refs: Option<Vec<Ref>>,
+    /// Shallow updates as part of the `Protocol::V1`, to shallow a particular object.
+    /// Note that unshallowing isn't supported here.
+    pub v1_shallow_updates: Option<Vec<ShallowUpdate>>,
     /// The server capabilities.
     pub capabilities: Capabilities,
 }
@@ -93,6 +96,7 @@ mod error {
         }
     }
 }
+use crate::fetch::response::ShallowUpdate;
 pub use error::Error;
 
 pub(crate) mod function;

gix-protocol/src/handshake/refs/async_io.rs

@@ -1,3 +1,4 @@
+use crate::fetch::response::ShallowUpdate;
 use crate::handshake::{refs, refs::parse::Error, Ref};
 
 /// Parse refs from the given input line by line. Protocol V2 is required for this to succeed.
@@ -26,8 +27,9 @@ pub async fn from_v2_refs(in_refs: &mut dyn gix_transport::client::ReadlineBufRe
 pub async fn from_v1_refs_received_as_part_of_handshake_and_capabilities<'a>(
     in_refs: &mut dyn gix_transport::client::ReadlineBufRead,
     capabilities: impl Iterator<Item = gix_transport::client::capabilities::Capability<'a>>,
-) -> Result<Vec<Ref>, refs::parse::Error> {
+) -> Result<(Vec<Ref>, Vec<ShallowUpdate>), refs::parse::Error> {
     let mut out_refs = refs::shared::from_capabilities(capabilities)?;
+    let mut out_shallow = Vec::new();
     let number_of_possible_symbolic_refs_for_lookup = out_refs.len();
 
     while let Some(line) = in_refs
@@ -37,7 +39,12 @@ pub async fn from_v1_refs_received_as_part_of_handshake_and_capabilities<'a>(
         .transpose()?
         .and_then(|l| l.as_bstr())
     {
-        refs::shared::parse_v1(number_of_possible_symbolic_refs_for_lookup, &mut out_refs, line)?;
+        refs::shared::parse_v1(
+            number_of_possible_symbolic_refs_for_lookup,
+            &mut out_refs,
+            &mut out_shallow,
+            line,
+        )?;
     }
-    Ok(out_refs.into_iter().map(Into::into).collect())
+    Ok((out_refs.into_iter().map(Into::into).collect(), out_shallow))
 }

gix-protocol/src/handshake/refs/blocking_io.rs

@@ -1,3 +1,4 @@
+use crate::fetch::response::ShallowUpdate;
 use crate::handshake::{refs, refs::parse::Error, Ref};
 
 /// Parse refs from the given input line by line. Protocol V2 is required for this to succeed.
@@ -20,12 +21,18 @@ pub fn from_v2_refs(in_refs: &mut dyn gix_transport::client::ReadlineBufRead) ->
 pub fn from_v1_refs_received_as_part_of_handshake_and_capabilities<'a>(
     in_refs: &mut dyn gix_transport::client::ReadlineBufRead,
     capabilities: impl Iterator<Item = gix_transport::client::capabilities::Capability<'a>>,
-) -> Result<Vec<Ref>, Error> {
+) -> Result<(Vec<Ref>, Vec<ShallowUpdate>), Error> {
     let mut out_refs = refs::shared::from_capabilities(capabilities)?;
+    let mut out_shallow = Vec::new();
     let number_of_possible_symbolic_refs_for_lookup = out_refs.len();
 
     while let Some(line) = in_refs.readline().transpose()?.transpose()?.and_then(|l| l.as_bstr()) {
-        refs::shared::parse_v1(number_of_possible_symbolic_refs_for_lookup, &mut out_refs, line)?;
+        refs::shared::parse_v1(
+            number_of_possible_symbolic_refs_for_lookup,
+            &mut out_refs,
+            &mut out_shallow,
+            line,
+        )?;
     }
-    Ok(out_refs.into_iter().map(Into::into).collect())
+    Ok((out_refs.into_iter().map(Into::into).collect(), out_shallow))
 }

gix-protocol/src/handshake/refs/shared.rs

@@ -1,3 +1,4 @@
+use crate::fetch::response::ShallowUpdate;
 use crate::handshake::{refs::parse::Error, Ref};
 use bstr::{BStr, BString, ByteSlice};
 
@@ -122,6 +123,7 @@ pub(crate) fn from_capabilities<'a>(
 pub(in crate::handshake::refs) fn parse_v1(
     num_initial_out_refs: usize,
     out_refs: &mut Vec<InternalRef>,
+    out_shallow: &mut Vec<ShallowUpdate>,
     line: &BStr,
 ) -> Result<(), Error> {
     let trimmed = line.trim_end();
@@ -162,7 +164,9 @@ pub(in crate::handshake::refs) fn parse_v1(
             let object = match gix_hash::ObjectId::from_hex(hex_hash.as_bytes()) {
                 Ok(id) => id,
                 Err(_) if hex_hash.as_bstr() == "shallow" => {
-                    todo!("shallow");
+                    let id = gix_hash::ObjectId::from_hex(path)?;
+                    out_shallow.push(ShallowUpdate::Shallow(id));
+                    return Ok(());
                 }
                 Err(err) => return Err(err.into()),
             };

gix-protocol/src/handshake/refs/tests.rs

@@ -79,7 +79,7 @@ dce0ea858eef7ff61ad345cc5cdac62203fb3c10 refs/tags/gix-commitgraph-v0.0.0
 21c9b7500cb144b3169a6537961ec2b9e865be81 refs/tags/gix-commitgraph-v0.0.0^{}"
             .as_bytes(),
     );
-    let out = refs::from_v1_refs_received_as_part_of_handshake_and_capabilities(
+    let (out, shallow) = refs::from_v1_refs_received_as_part_of_handshake_and_capabilities(
         input,
         Capabilities::from_bytes(b"\0symref=HEAD:refs/heads/main symref=MISSING_NAMESPACE_TARGET:(null)")
             .expect("valid capabilities")
@@ -88,6 +88,7 @@ dce0ea858eef7ff61ad345cc5cdac62203fb3c10 refs/tags/gix-commitgraph-v0.0.0
     )
     .await
     .expect("no failure from valid input");
+    assert!(shallow.is_empty());
     assert_eq!(
         out,
         vec![
@@ -120,6 +121,7 @@ dce0ea858eef7ff61ad345cc5cdac62203fb3c10 refs/tags/gix-commitgraph-v0.0.0
 
 #[maybe_async::test(feature = "blocking-client", async(feature = "async-client", async_std::test))]
 async fn extract_references_from_v1_refs_with_shallow() {
+    use crate::fetch::response::ShallowUpdate;
     let input = &mut Fixture(
         "73a6868963993a3328e7d8fe94e5a6ac5078a944 HEAD
 21c9b7500cb144b3169a6537961ec2b9e865be81 MISSING_NAMESPACE_TARGET
@@ -131,7 +133,7 @@ shallow 21c9b7500cb144b3169a6537961ec2b9e865be81
 shallow dce0ea858eef7ff61ad345cc5cdac62203fb3c10"
             .as_bytes(),
     );
-    let out = refs::from_v1_refs_received_as_part_of_handshake_and_capabilities(
+    let (out, shallow) = refs::from_v1_refs_received_as_part_of_handshake_and_capabilities(
         input,
         Capabilities::from_bytes(b"\0symref=HEAD:refs/heads/main symref=MISSING_NAMESPACE_TARGET:(null)")
             .expect("valid capabilities")
@@ -140,6 +142,14 @@ shallow dce0ea858eef7ff61ad345cc5cdac62203fb3c10"
     )
     .await
     .expect("no failure from valid input");
+
+    assert_eq!(
+        shallow,
+        vec![
+            ShallowUpdate::Shallow(oid("21c9b7500cb144b3169a6537961ec2b9e865be81")),
+            ShallowUpdate::Shallow(oid("dce0ea858eef7ff61ad345cc5cdac62203fb3c10"))
+        ]
+    );
     assert_eq!(
         out,
         vec![