feat: make lockfile v4 the default

This commit makes lockfile version 4 the default version when Cargo
tries to write to a lockfile.

The lockfile version 4 has been stabilized since 1.78.0,
and will become default in 1.83.0.
the length of transition period is pretty similar as before.

One caveat is that in other output from Cargo,
e.g., `cargo metatada`, status messages,
`SourceID` will display in the v4 URL encoded format.
This shouldn't affect the majority of Rust users,
as `SourceId` representation should be opaque to them,
unless comparing `SourceId` across different version of toolchains.

src/cargo/core/resolver/resolve.rs

@@ -84,13 +84,14 @@ pub enum ResolveVersion {
     /// branch specifiers.
     ///
     /// * Introduced in 2020 in version 1.47.
-    /// * New lockfiles use V3 by default starting in 1.53.
+    /// * New lockfiles use V3 by default from in 1.53 to 1.82.
     V3,
     /// SourceId URL serialization is aware of URL encoding. For example,
     /// `?branch=foo bar` is now encoded as `?branch=foo+bar` and can be decoded
     /// back and forth correctly.
     ///
     /// * Introduced in 2024 in version 1.78.
+    /// * New lockfiles use V4 by default starting in 1.83.
     V4,
     /// Unstable. Will collect a certain amount of changes and then go.
     ///
@@ -107,7 +108,7 @@ impl ResolveVersion {
     /// Update this and the description of enum variants of [`ResolveVersion`]
     /// when we're changing the default lockfile version.
     fn default() -> ResolveVersion {
-        ResolveVersion::V3
+        ResolveVersion::V4
     }
 
     /// The maximum version of lockfile made into the stable channel.
@@ -137,7 +138,9 @@ impl ResolveVersion {
             .unwrap()
         };
 
-        if rust_version >= &rust(1, 53) {
+        if rust_version >= &rust(1, 83) {
+            ResolveVersion::V4
+        } else if rust_version >= &rust(1, 53) {
             ResolveVersion::V3
         } else if rust_version >= &rust(1, 41) {
             ResolveVersion::V2

src/cargo/core/source_id.rs

@@ -644,10 +644,7 @@ impl fmt::Display for SourceId {
                 // Don't replace the URL display for git references,
                 // because those are kind of expected to be URLs.
                 write!(f, "{}", self.inner.url)?;
-                // TODO(-Znext-lockfile-bump): set it to true when the default is
-                // lockfile v4, because we want Source ID serialization to be
-                // consistent with lockfile.
-                if let Some(pretty) = reference.pretty_ref(false) {
+                if let Some(pretty) = reference.pretty_ref(true) {
                     write!(f, "?{}", pretty)?;
                 }
 

src/cargo/sources/git/source.rs

@@ -226,12 +226,8 @@ fn ident_shallow(id: &SourceId, is_shallow: bool) -> String {
 impl<'gctx> Debug for GitSource<'gctx> {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         write!(f, "git repo at {}", self.remote.url())?;
-
-        // TODO(-Znext-lockfile-bump): set it to true when the default is
-        // lockfile v4, because we want Source ID serialization to be
-        // consistent with lockfile.
         match &self.locked_rev {
-            Revision::Deferred(git_ref) => match git_ref.pretty_ref(false) {
+            Revision::Deferred(git_ref) => match git_ref.pretty_ref(true) {
                 Some(s) => write!(f, " ({})", s),
                 None => Ok(()),
             },

src/cargo/util/toml_mut/dependency.rs

@@ -1002,11 +1002,7 @@ impl GitSource {
 impl std::fmt::Display for GitSource {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let git_ref = self.git_ref();
-
-        // TODO(-Znext-lockfile-bump): set it to true when the default is
-        // lockfile v4, because we want Source ID serialization to be
-        // consistent with lockfile.
-        if let Some(pretty_ref) = git_ref.pretty_ref(false) {
+        if let Some(pretty_ref) = git_ref.pretty_ref(true) {
             write!(f, "{}?{}", self.git, pretty_ref)
         } else {
             write!(f, "{}", self.git)

tests/testsuite/alt_registry.rs

@@ -1790,7 +1790,7 @@ fn sparse_lockfile() {
         str![[r##"
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "a"

tests/testsuite/git.rs

@@ -283,7 +283,7 @@ fn cargo_compile_git_dep_pull_request() {
         .with_stderr_data(str![[r#"
 [UPDATING] git repository `[ROOTURL]/dep1`
 [LOCKING] 1 package to latest compatible version
-[COMPILING] dep1 v0.5.0 ([ROOTURL]/dep1?rev=refs/pull/330/head#[..])
+[COMPILING] dep1 v0.5.0 ([ROOTURL]/dep1?rev=refs%2Fpull%2F330%2Fhead#[..])
 [COMPILING] foo v0.0.0 ([ROOT]/foo)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
 

tests/testsuite/lockfile_compat.rs

@@ -21,7 +21,7 @@ fn oldest_lockfile_still_works_with_command(cargo_command: &str) {
     let expected_lockfile = str![[r##"
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "bar"
@@ -173,7 +173,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
         str![[r##"
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "bar"
@@ -407,7 +407,7 @@ fn current_lockfile_format() {
     let expected = str![[r##"
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "bar"
@@ -473,7 +473,7 @@ dependencies = [
         str![[r##"
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "bar"
@@ -682,7 +682,7 @@ dependencies = [
                     name = "foo"
                     version = "0.0.1"
                     edition = "2015"
-                    authors = []
+                    rust-version = "1.82"
 
                     [dependencies]
                     dep1 = {{ git = '{}', branch = 'master' }}
@@ -937,38 +937,6 @@ Caused by:
         .run();
 }
 
-#[cargo_test]
-fn v4_cannot_be_created_from_scratch() {
-    let p = project()
-        .file(
-            "Cargo.toml",
-            &format!(
-                r#"
-                    [package]
-                    name = "foo"
-                    version = "0.0.1"
-                    edition = "2015"
-                "#,
-            ),
-        )
-        .file("src/lib.rs", "")
-        .build();
-
-    p.cargo("fetch").run();
-
-    let lockfile = r#"# This file is automatically @generated by Cargo.
-# It is not intended for manual editing.
-version = 3
-
-[[package]]
-name = "foo"
-version = "0.0.1"
-"#;
-
-    let lock = p.read_lockfile();
-    assert_e2e().eq(&lock, lockfile);
-}
-
 fn create_branch(repo: &git2::Repository, branch: &str, head_id: git2::Oid) {
     repo.branch(branch, &repo.find_commit(head_id).unwrap(), true)
         .unwrap();
@@ -995,6 +963,7 @@ fn v3_and_git_url_encoded(ref_kind: &str, f: impl FnOnce(&git2::Repository, &str
     let head_id = repo.head().unwrap().target().unwrap();
     // Ref name with special characters
     let git_ref = "a-_+#$)";
+    let encoded_ref = "a-_%2B%23%24%29";
     f(&repo, git_ref, head_id);
 
     let lockfile = format!(
@@ -1025,6 +994,7 @@ dependencies = [
                     name = "foo"
                     version = "0.0.1"
                     edition = "2015"
+                    rust-version = "1.82" # ensure it stays in lockfile v3
 
                     [dependencies]
                     dep1 = {{ git = '{url}', {ref_kind} = '{git_ref}' }}
@@ -1040,8 +1010,8 @@ dependencies = [
             "\
 [UPDATING] git repository `[ROOTURL]/dep1`
 [LOCKING] 1 package to latest compatible version
-[ADDING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={git_ref}#[..])
-[CHECKING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={git_ref}#[..])
+[ADDING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={encoded_ref}#[..])
+[CHECKING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={encoded_ref}#[..])
 [CHECKING] foo v0.0.1 ([ROOT]/foo)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
 "
@@ -1135,8 +1105,8 @@ dependencies = [
             "\
 [UPDATING] git repository `[ROOTURL]/dep1`
 [LOCKING] 1 package to latest compatible version
-[ADDING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={git_ref}#[..])
-[CHECKING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={git_ref}#[..])
+[ADDING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={encoded_ref}#[..])
+[CHECKING] dep1 v0.5.0 ([ROOTURL]/dep1?{ref_kind}={encoded_ref}#[..])
 [CHECKING] foo v0.0.1 ([ROOT]/foo)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
 "
@@ -1281,7 +1251,7 @@ dependencies = [
         // last version of v3 as the default
         ("1.82", None, 3),
         // v4 is the default
-        ("1.83", None, 3),
+        ("1.83", None, 4),
         ("1.83", Some(1), 1),
         ("1.83", Some(2), 2),
         ("1.83", Some(3), 3),