Allow precise update to prerelease.

src/cargo/core/dependency.rs

@@ -402,6 +402,14 @@ impl Dependency {
         self.matches_id(sum.package_id())
     }
 
+    pub fn matches_prerelease(&self, sum: &Summary) -> bool {
+        let id = sum.package_id();
+        self.inner.name == id.name()
+            && (self.inner.only_match_name
+                || (self.inner.req.matches_prerelease(id.version())
+                    && self.inner.source_id == id.source_id()))
+    }
+
     /// Returns `true` if the package (`id`) can fulfill this dependency request.
     pub fn matches_ignoring_source(&self, id: PackageId) -> bool {
         self.package_name() == id.name() && self.version_req().matches(id.version())

src/cargo/core/features.rs

@@ -773,7 +773,6 @@ unstable_cli_options!(
     next_lockfile_bump: bool,
     no_index_update: bool = ("Do not update the registry index even if the cache is outdated"),
     panic_abort_tests: bool = ("Enable support to run tests with -Cpanic=abort"),
-    precise_pre_release: bool = ("Enable pre-release versions to be selected with `update --precise`"),
     profile_rustflags: bool = ("Enable the `rustflags` option in profiles in .cargo/config.toml file"),
     public_dependency: bool = ("Respect a dependency's `public` field in Cargo.toml to control public/private dependencies"),
     publish_timeout: bool = ("Enable the `publish.timeout` key in .cargo/config.toml file"),
@@ -1154,7 +1153,6 @@ impl CliUnstable {
             "panic-abort-tests" => self.panic_abort_tests = parse_empty(k, v)?,
             "public-dependency" => self.public_dependency = parse_empty(k, v)?,
             "profile-rustflags" => self.profile_rustflags = parse_empty(k, v)?,
-            "precise-pre-release" => self.precise_pre_release = parse_empty(k, v)?,
             "trim-paths" => self.trim_paths = parse_empty(k, v)?,
             "publish-timeout" => self.publish_timeout = parse_empty(k, v)?,
             "rustdoc-map" => self.rustdoc_map = parse_empty(k, v)?,

src/cargo/sources/registry/mod.rs

@@ -208,9 +208,9 @@ use crate::sources::source::QueryKind;
 use crate::sources::source::Source;
 use crate::sources::PathSource;
 use crate::util::cache_lock::CacheLockMode;
-use crate::util::hex;
 use crate::util::interning::InternedString;
 use crate::util::network::PollExt;
+use crate::util::{hex, VersionExt};
 use crate::util::{restricted_names, CargoResult, Filesystem, GlobalContext, LimitErrorReader};
 
 /// The `.cargo-ok` file is used to track if the source is already unpacked.
@@ -752,7 +752,13 @@ impl<'gctx> Source for RegistrySource<'gctx> {
         if let Some((_, requested)) = self
             .source_id
             .precise_registry_version(dep.package_name().as_str())
-            .filter(|(c, _)| req.matches(c))
+            .filter(|(c, to)| {
+                if to.is_prerelease() && self.gctx.cli_unstable().unstable_options {
+                    req.matches_prerelease(c)
+                } else {
+                    req.matches(c)
+                }
+            })
         {
             req.precise_to(&requested);
         }
@@ -790,7 +796,13 @@ impl<'gctx> Source for RegistrySource<'gctx> {
                 .index
                 .query_inner(dep.package_name(), &req, &mut *self.ops, &mut |s| {
                     let matched = match kind {
-                        QueryKind::Exact => dep.matches(s.as_summary()),
+                        QueryKind::Exact => {
+                            if req.is_precise() && self.gctx.cli_unstable().unstable_options {
+                                dep.matches_prerelease(s.as_summary())
+                            } else {
+                                dep.matches(s.as_summary())
+                            }
+                        }
                         QueryKind::Alternatives => true,
                         QueryKind::Normalized => true,
                     };

src/cargo/util/semver_ext.rs

@@ -111,6 +111,19 @@ impl OptVersionReq {
         }
     }
 
+    /// Since Semver does not support prerelease versions,
+    /// the simplest implementation is taken here without comparing the prerelease section.
+    /// The logic here is temporary, we'll have to consider more boundary conditions later,
+    /// and we're not sure if this part of the functionality should be implemented in semver or cargo.
+    pub fn matches_prerelease(&self, version: &Version) -> bool {
+        if version.is_prerelease() {
+            let mut version = version.clone();
+            version.pre = semver::Prerelease::EMPTY;
+            return self.matches(&version);
+        }
+        self.matches(version)
+    }
+
     pub fn matches(&self, version: &Version) -> bool {
         match self {
             OptVersionReq::Any => true,

src/doc/man/cargo-update.md

@@ -46,6 +46,8 @@ revision (such as a SHA hash or tag).
 While not recommended, you can specify a yanked version of a package (nightly only).
 When possible, try other non-yanked SemVer-compatible versions or seek help
 from the maintainers of the package.
+
+A compatible `pre-release` version can also be specified even when the version requirement in `Cargo.toml` doesn't contain any pre-release identifer (nightly only).
 {{/option}}
 
 {{#option "`-w`" "`--workspace`" }}

src/doc/man/generated_txt/cargo-update.txt

@@ -40,6 +40,10 @@ OPTIONS
            SemVer-compatible versions or seek help from the maintainers of the
            package.
 
+           A compatible pre-release version can also be specified even when the
+           version requirement in Cargo.toml doesn’t contain any pre-release
+           identifer (nightly only).
+
        -w, --workspace
            Attempt to update only packages defined in the workspace. Other
            packages are updated only if they don’t already exist in the

src/doc/src/commands/cargo-update.md

@@ -42,7 +42,8 @@ the package to. If the package comes from a git repository, this can be a git
 revision (such as a SHA hash or tag).</p>
 <p>While not recommended, you can specify a yanked version of a package (nightly only).
 When possible, try other non-yanked SemVer-compatible versions or seek help
-from the maintainers of the package.</dd>
+from the maintainers of the package.</p>
+<p>A compatible <code>pre-release</code> version can also be specified even when the version requirement in <code>Cargo.toml</code> doesn’t contain any pre-release identifer (nightly only).</dd>
 
 
 <dt class="option-term" id="option-cargo-update--w"><a class="option-anchor" href="#option-cargo-update--w"></a><code>-w</code></dt>

src/doc/src/reference/unstable.md

@@ -347,7 +347,7 @@ Take for example this `Cargo.toml`.
 my-dependency = "0.1.1"
 ```
 
-It's possible to update `my-dependancy` to a pre-release with `update -Zprecise-pre-release -p my-dependency --precise 0.1.2-pre.0`.
+It's possible to update `my-dependancy` to a pre-release with `update -Zunstable-options my-dependency --precise 0.1.2-pre.0`.
 This is because `0.1.2-pre.0` is considered compatible with `0.1.1`.
 It would not be possible to upgrade to `0.2.0-pre.0` from `0.1.1` in the same way.
 

src/etc/man/cargo-update.1

@@ -43,6 +43,8 @@ revision (such as a SHA hash or tag).
 While not recommended, you can specify a yanked version of a package (nightly only).
 When possible, try other non\-yanked SemVer\-compatible versions or seek help
 from the maintainers of the package.
+.sp
+A compatible \fBpre\-release\fR version can also be specified even when the version requirement in \fBCargo.toml\fR doesn\[cq]t contain any pre\-release identifer (nightly only).
 .RE
 .sp
 \fB\-w\fR, 

tests/testsuite/precise_pre_release.rs

@@ -23,7 +23,7 @@ fn requires_nightly_cargo() {
         .file("src/lib.rs", "")
         .build();
 
-    p.cargo("update -p my-dependency --precise 0.1.2-pre.0")
+    p.cargo("update my-dependency --precise 0.1.2-pre.0")
         .with_status(101)
         // This error is suffering from #12579 but still demonstrates that updating to
         // a pre-release does not work on stable
@@ -41,20 +41,77 @@ perhaps a crate was updated and forgotten to be re-vendored?"#,
 }
 
 #[cargo_test]
-fn feature_exists() {
+fn update_pre_release() {
+    cargo_test_support::registry::init();
+
+    for version in ["0.1.1", "0.1.2-pre.0"] {
+        cargo_test_support::registry::Package::new("my-dependency", version).publish();
+    }
+
     let p = project()
         .file(
             "Cargo.toml",
             r#"
             [package]
             name = "package"
+            [dependencies]
+            my-dependency = "0.1.1"
             "#,
         )
         .file("src/lib.rs", "")
         .build();
 
-    p.cargo("-Zprecise-pre-release update")
+    p.cargo("update my-dependency --precise 0.1.2-pre.0 -Zunstable-options")
         .masquerade_as_nightly_cargo(&["precise-pre-release"])
-        .with_stderr("")
-        .run()
+        .with_stderr(
+            r#"[UPDATING] `dummy-registry` index
+[UPDATING] my-dependency v0.1.1 -> v0.1.2-pre.0
+"#,
+        )
+        .run();
+    let lockfile = p.read_lockfile();
+    assert!(lockfile.contains("\nname = \"my-dependency\"\nversion = \"0.1.2-pre.0\""));
+}
+
+#[cargo_test]
+fn update_pre_release_differ() {
+    cargo_test_support::registry::init();
+
+    for version in ["0.1.2", "0.1.2-pre.0", "0.1.2-pre.1"] {
+        cargo_test_support::registry::Package::new("my-dependency", version).publish();
+    }
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "package"
+            [dependencies]
+            my-dependency = "0.1.2"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("update -p my-dependency --precise 0.1.2-pre.0 -Zunstable-options")
+        .masquerade_as_nightly_cargo(&["precise-pre-release"])
+        .with_stderr(
+            r#"[UPDATING] `dummy-registry` index
+[DOWNGRADING] my-dependency v0.1.2 -> v0.1.2-pre.0
+"#,
+        )
+        .run();
+
+    p.cargo("update -p my-dependency --precise 0.1.2-pre.1 -Zunstable-options")
+        .masquerade_as_nightly_cargo(&["precise-pre-release"])
+        .with_stderr(
+            r#"[UPDATING] `dummy-registry` index
+[UPDATING] my-dependency v0.1.2-pre.0 -> v0.1.2-pre.1
+"#,
+        )
+        .run();
+
+    let lockfile = p.read_lockfile();
+    assert!(lockfile.contains("\nname = \"my-dependency\"\nversion = \"0.1.2-pre.1\""));
 }