Only override resolver when the workspace is different

Author: Nemo157

src/cargo/core/features.rs

@@ -102,6 +102,7 @@ use anyhow::{bail, Error};
 use cargo_util::ProcessBuilder;
 use serde::{Deserialize, Serialize};
 
+use crate::core::resolver::ResolveBehavior;
 use crate::util::errors::CargoResult;
 use crate::util::{indented_lines, iter_join};
 use crate::Config;
@@ -242,6 +243,14 @@ impl Edition {
             Edition2021 => false,
         }
     }
+
+    pub(crate) fn default_resolve_behavior(&self) -> ResolveBehavior {
+        if *self >= Edition::Edition2021 {
+            ResolveBehavior::V2
+        } else {
+            ResolveBehavior::V1
+        }
+    }
 }
 
 impl fmt::Display for Edition {

src/cargo/core/workspace.rs

@@ -16,7 +16,7 @@ use crate::core::features::Features;
 use crate::core::registry::PackageRegistry;
 use crate::core::resolver::features::CliFeatures;
 use crate::core::resolver::ResolveBehavior;
-use crate::core::{Dependency, Edition, FeatureValue, PackageId, PackageIdSpec};
+use crate::core::{Dependency, FeatureValue, PackageId, PackageIdSpec};
 use crate::core::{EitherManifest, Package, SourceId, VirtualManifest};
 use crate::ops;
 use crate::sources::{PathSource, CRATES_IO_INDEX, CRATES_IO_REGISTRY};
@@ -287,16 +287,12 @@ impl<'cfg> Workspace<'cfg> {
         // - If the root package specifies edition 2021, use v2.
         // - Otherwise, use the default v1.
         self.resolve_behavior = match self.root_maybe() {
-            MaybePackage::Package(p) => p.manifest().resolve_behavior().or_else(|| {
-                if p.manifest().edition() >= Edition::Edition2021 {
-                    Some(ResolveBehavior::V2)
-                } else {
-                    None
-                }
-            }),
-            MaybePackage::Virtual(vm) => vm.resolve_behavior(),
+            MaybePackage::Package(p) => p
+                .manifest()
+                .resolve_behavior()
+                .or_else(|| p.manifest().edition().default_resolve_behavior()),
+            MaybePackage::Virtual(vm) => vm.resolve_behavior().unwrap_or(ResolveBehavior::V1),
         }
-        .unwrap_or(ResolveBehavior::V1);
     }
 
     /// Returns the current package of this workspace.

src/cargo/util/toml/mod.rs

@@ -3,7 +3,7 @@ use std::fmt;
 use std::marker::PhantomData;
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
-use std::str;
+use std::str::{self, FromStr};
 
 use anyhow::{anyhow, bail, Context as _};
 use cargo_platform::Platform;
@@ -1342,7 +1342,22 @@ impl TomlManifest {
             .unwrap()
             .clone();
         package.workspace = None;
-        package.resolver = Some(ws.resolve_behavior().to_manifest());
+        let current_resolver = package
+            .resolver
+            .as_ref()
+            .map(|r| ResolveBehavior::from_manifest(r))
+            .unwrap_or_else(|| {
+                package
+                    .edition
+                    .as_ref()
+                    .and_then(|e| e.as_defined())
+                    .map(|e| Edition::from_str(e))
+                    .transpose()
+                    .map(|e| e.unwrap_or(Edition::Edition2015).default_resolve_behavior())
+            })?;
+        if ws.resolve_behavior() != current_resolver {
+            package.resolver = Some(ws.resolve_behavior().to_manifest());
+        }
         if let Some(license_file) = &package.license_file {
             let license_file = license_file
                 .as_defined()