feat(resolve): Direct people to working around less optimal MSRV-resolver results

In discussing #14414, the general problem of the resolver picking a
version older than a package needs for its MSRV (or lack of one) because of the MSRV of
other packages came up.
This tries to patch over that problem by telling users that a dependency
might be able to be newer than the resolver selected.

The message is fairly generic and might be misread to be about any MSRV
update which an MSRV `fallback` strategy allows, which would make the
count off.
The reason it is so generic is we don't know with precision why it was
held back
- Direct dependents may have a non-semver upper bound on the version as
  we aren't trying to unify the version requirements across direct
  dependents at this time
- A dependency could have removed a feature without making a breaking
  change
  - This seems like it should instead be an error but thats a
    conversation for another day
- ~~The user enabled `-Zminimal-versions`~~
  - This is now detected and the message skipped

Note: separate from this, we may also print the status suffix for this
case if the package was not selected for update (e.g. passing
`--workspace`).

Author: epage

src/cargo/ops/cargo_update.rs

@@ -519,6 +519,7 @@ fn print_lockfile_generation(
     annotate_required_rust_version(ws, resolve, &mut changes);
 
     status_locking(ws, num_pkgs)?;
+    let mut changed_stats = UpdateStats::default();
     for change in changes.values() {
         if change.is_member.unwrap_or(false) {
             continue;
@@ -538,8 +539,9 @@ fn print_lockfile_generation(
                     vec![]
                 };
 
-                let required_rust_version = report_required_rust_version(resolve, change, None);
-                let latest = report_latest(&possibilities, change, None);
+                let required_rust_version =
+                    report_required_rust_version(resolve, change, Some(&mut changed_stats));
+                let latest = report_latest(&possibilities, change, Some(&mut changed_stats));
                 let note = required_rust_version.or(latest);
 
                 if let Some(note) = note {
@@ -559,6 +561,22 @@ fn print_lockfile_generation(
         }
     }
 
+    let compat_ver_compat_msrv = changed_stats.compat_ver_compat_msrv;
+    if 0 < compat_ver_compat_msrv
+        && !ws.gctx().cli_unstable().direct_minimal_versions
+        && !ws.gctx().cli_unstable().minimal_versions
+    {
+        if compat_ver_compat_msrv == 1 {
+            ws.gctx().shell().note(format!(
+                "{compat_ver_compat_msrv} package may have a higher, compatible versions. To update it, run `cargo update <name> --precise <version>"
+            ))?;
+        } else {
+            ws.gctx().shell().note(format!(
+                "{compat_ver_compat_msrv} packages may have higher, compatible versions. To update them, run `cargo update <name> --precise <version>"
+            ))?;
+        }
+    }
+
     Ok(())
 }
 
@@ -580,6 +598,7 @@ fn print_lockfile_sync(
     annotate_required_rust_version(ws, resolve, &mut changes);
 
     status_locking(ws, num_pkgs)?;
+    let mut changed_stats = UpdateStats::default();
     for change in changes.values() {
         if change.is_member.unwrap_or(false) {
             continue;
@@ -601,8 +620,9 @@ fn print_lockfile_sync(
                     vec![]
                 };
 
-                let required_rust_version = report_required_rust_version(resolve, change, None);
-                let latest = report_latest(&possibilities, change, None);
+                let required_rust_version =
+                    report_required_rust_version(resolve, change, Some(&mut changed_stats));
+                let latest = report_latest(&possibilities, change, Some(&mut changed_stats));
                 let note = required_rust_version.or(latest).unwrap_or_default();
 
                 ws.gctx().shell().status_with_color(
@@ -615,6 +635,16 @@ fn print_lockfile_sync(
         }
     }
 
+    let compat_ver_compat_msrv = changed_stats.compat_ver_compat_msrv;
+    if 0 < compat_ver_compat_msrv
+        && !ws.gctx().cli_unstable().direct_minimal_versions
+        && !ws.gctx().cli_unstable().minimal_versions
+    {
+        ws.gctx().shell().note(format!(
+                "{compat_ver_compat_msrv} were updated but higher versions may be available by manually updating with `cargo update <name> --precise <version>"
+            ))?;
+    }
+
     Ok(())
 }
 
@@ -636,6 +666,7 @@ fn print_lockfile_updates(
         status_locking(ws, num_pkgs)?;
     }
     let mut unchanged_behind = 0;
+    let mut changed_stats = UpdateStats::default();
     for change in changes.values() {
         let possibilities = if let Some(query) = change.alternatives_query() {
             loop {
@@ -654,8 +685,9 @@ fn print_lockfile_updates(
             PackageChangeKind::Added
             | PackageChangeKind::Upgraded
             | PackageChangeKind::Downgraded => {
-                let required_rust_version = report_required_rust_version(resolve, change, None);
-                let latest = report_latest(&possibilities, change, None);
+                let required_rust_version =
+                    report_required_rust_version(resolve, change, Some(&mut changed_stats));
+                let latest = report_latest(&possibilities, change, Some(&mut changed_stats));
                 let note = required_rust_version.or(latest).unwrap_or_default();
 
                 ws.gctx().shell().status_with_color(
@@ -694,6 +726,15 @@ fn print_lockfile_updates(
         }
     }
 
+    let compat_ver_compat_msrv = changed_stats.compat_ver_compat_msrv;
+    if 0 < compat_ver_compat_msrv
+        && !ws.gctx().cli_unstable().direct_minimal_versions
+        && !ws.gctx().cli_unstable().minimal_versions
+    {
+        ws.gctx().shell().note(format!(
+                "{compat_ver_compat_msrv} were updated but higher versions may be available by manually updating with `cargo update <name> --precise <version>"
+            ))?;
+    }
     if ws.gctx().shell().verbosity() == Verbosity::Verbose {
         ws.gctx().shell().note(
             "to see how you depend on a package, run `cargo tree --invert --package <dep>@<ver>`",
@@ -886,7 +927,7 @@ fn report_latest(
     }
 }
 
-#[derive(Default)]
+#[derive(Copy, Clone, Default, Debug)]
 struct UpdateStats {
     required_rust_version: usize,
     compat_ver_compat_msrv: usize,

tests/testsuite/rust_version.rs

@@ -1214,6 +1214,7 @@ fn report_rust_versions() {
 [ADDING] dep-only-unset-compatible v1.55.0 (available: v1.75.0)
 [ADDING] dep-only-unset-incompatible v1.2345.0 (requires Rust 1.2345.0)
 [ADDING] dep-shared-incompatible v1.75.0 (requires Rust 1.75.0)
+[NOTE] 2 packages may have higher, compatible versions. To update them, run `cargo update <name> --precise <version>
 
 "#]])
         .run();

tests/testsuite/workspaces.rs

@@ -698,6 +698,7 @@ fn share_dependencies() {
 [UPDATING] `dummy-registry` index
 [LOCKING] 1 package to latest compatible version
 [ADDING] dep1 v0.1.3 (available: v0.1.8)
+[NOTE] 1 package may have a higher, compatible versions. To update it, run `cargo update <name> --precise <version>
 [DOWNLOADING] crates ...
 [DOWNLOADED] dep1 v0.1.3 (registry `dummy-registry`)
 [CHECKING] dep1 v0.1.3