refactor(msrv): Allow overriding MSRV-aware resolver

Author: epage

src/cargo/core/workspace.rs

@@ -103,7 +103,7 @@ pub struct Workspace<'gctx> {
 
     /// The resolver behavior specified with the `resolver` field.
     resolve_behavior: ResolveBehavior,
-    resolve_honors_rust_version: bool,
+    resolve_honors_rust_version: Option<bool>,
     honor_rust_version: Option<bool>,
 
     /// Workspace-level custom metadata
@@ -234,7 +234,7 @@ impl<'gctx> Workspace<'gctx> {
             loaded_packages: RefCell::new(HashMap::new()),
             ignore_lock: false,
             resolve_behavior: ResolveBehavior::V1,
-            resolve_honors_rust_version: false,
+            resolve_honors_rust_version: None,
             honor_rust_version: None,
             custom_metadata: None,
         }
@@ -310,7 +310,7 @@ impl<'gctx> Workspace<'gctx> {
             ResolveBehavior::V1 | ResolveBehavior::V2 => {}
             ResolveBehavior::V3 => {
                 if self.resolve_behavior == ResolveBehavior::V3 {
-                    self.resolve_honors_rust_version = true;
+                    self.resolve_honors_rust_version = Some(true);
                 }
             }
         }
@@ -320,7 +320,7 @@ impl<'gctx> Workspace<'gctx> {
             }) => {
                 if self.gctx().cli_unstable().msrv_policy {
                     self.resolve_honors_rust_version =
-                        precedence == CargoResolverPrecedence::SomethingLikeRustVersion;
+                        Some(precedence == CargoResolverPrecedence::SomethingLikeRustVersion);
                 } else {
                     self.gctx()
                         .shell()
@@ -660,7 +660,8 @@ impl<'gctx> Workspace<'gctx> {
     pub fn resolve_honors_rust_version(&self) -> bool {
         // Give CLI precedence
         self.honor_rust_version
-            .unwrap_or(self.resolve_honors_rust_version)
+            .or(self.resolve_honors_rust_version)
+            .unwrap_or(false)
     }
 
     pub fn custom_metadata(&self) -> Option<&toml::Value> {