Override to resolver=1 in published package

src/cargo/core/resolver/types.rs

@@ -119,11 +119,12 @@ impl ResolveBehavior {
         }
     }
 
-    pub fn to_manifest(&self) -> Option<String> {
+    pub fn to_manifest(&self) -> String {
         match self {
-            ResolveBehavior::V1 => None,
-            ResolveBehavior::V2 => Some("2".to_string()),
+            ResolveBehavior::V1 => "1",
+            ResolveBehavior::V2 => "2",
         }
+        .to_owned()
     }
 }
 

src/cargo/util/toml/mod.rs

@@ -1342,7 +1342,7 @@ impl TomlManifest {
             .unwrap()
             .clone();
         package.workspace = None;
-        package.resolver = ws.resolve_behavior().to_manifest();
+        package.resolver = Some(ws.resolve_behavior().to_manifest());
         if let Some(license_file) = &package.license_file {
             let license_file = license_file
                 .as_defined()

tests/testsuite/package.rs

@@ -2325,3 +2325,46 @@ See [..]
     assert!(p.root().join("target/package/foo-0.0.1.crate").is_file());
     assert!(p.root().join("target/package/bar-0.0.1.crate").is_file());
 }
+
+#[cargo_test]
+fn workspace_overrides_resolver() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [workspace]
+                members = ["bar"]
+            "#,
+        )
+        .file(
+            "bar/Cargo.toml",
+            r#"
+                [package]
+                name = "bar"
+                version = "0.1.0"
+                edition = "2021"
+            "#,
+        )
+        .file("bar/src/lib.rs", "")
+        .build();
+
+    p.cargo("package --no-verify").cwd("bar").run();
+
+    let f = File::open(&p.root().join("target/package/bar-0.1.0.crate")).unwrap();
+    let rewritten_toml = format!(
+        r#"{}
+[package]
+edition = "2021"
+name = "bar"
+version = "0.1.0"
+resolver = "1"
+"#,
+        cargo::core::package::MANIFEST_PREAMBLE
+    );
+    validate_crate_contents(
+        f,
+        "bar-0.1.0.crate",
+        &["Cargo.toml", "Cargo.toml.orig", "src/lib.rs"],
+        &[("Cargo.toml", &rewritten_toml)],
+    );
+}