refactor: Track when MSRV is explicitly set, either way

This will hopefully help when merging between CLI and config with rust-lang#13540.

src/bin/cargo/commands/add.rs

@@ -205,8 +205,7 @@ pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
 
     let dependencies = parse_dependencies(gctx, args)?;
 
-    let ignore_rust_version = args.flag("ignore-rust-version");
-    let honor_rust_version = !ignore_rust_version;
+    let honor_rust_version = args.honor_rust_version();
 
     let options = AddOptions {
         gctx,

src/cargo/ops/cargo_add/mod.rs

@@ -55,7 +55,7 @@ pub struct AddOptions<'a> {
     /// Act as if dependencies will be added
     pub dry_run: bool,
     /// Whether the minimum supported Rust version should be considered during resolution
-    pub honor_rust_version: bool,
+    pub honor_rust_version: Option<bool>,
 }
 
 /// Add dependencies to a manifest
@@ -288,7 +288,7 @@ fn resolve_dependency(
     ws: &Workspace<'_>,
     spec: &Package,
     section: &DepTable,
-    honor_rust_version: bool,
+    honor_rust_version: Option<bool>,
     gctx: &GlobalContext,
     registry: &mut PackageRegistry<'_>,
 ) -> CargoResult<DependencyUI> {
@@ -571,7 +571,7 @@ fn get_existing_dependency(
 fn get_latest_dependency(
     spec: &Package,
     dependency: &Dependency,
-    honor_rust_version: bool,
+    honor_rust_version: Option<bool>,
     gctx: &GlobalContext,
     registry: &mut PackageRegistry<'_>,
 ) -> CargoResult<Dependency> {
@@ -608,7 +608,7 @@ fn get_latest_dependency(
                 )
             })?;
 
-            if honor_rust_version {
+            if honor_rust_version.unwrap_or(true) {
                 let (req_msrv, is_msrv) = spec
                     .rust_version()
                     .cloned()

src/cargo/ops/cargo_compile/mod.rs

@@ -98,7 +98,7 @@ pub struct CompileOptions {
     pub rustdoc_document_private_items: bool,
     /// Whether the build process should check the minimum Rust version
     /// defined in the cargo metadata for a crate.
-    pub honor_rust_version: bool,
+    pub honor_rust_version: Option<bool>,
 }
 
 impl CompileOptions {
@@ -116,7 +116,7 @@ impl CompileOptions {
             target_rustc_args: None,
             target_rustc_crate_types: None,
             rustdoc_document_private_items: false,
-            honor_rust_version: true,
+            honor_rust_version: None,
         })
     }
 }
@@ -474,7 +474,7 @@ pub fn create_bcx<'a, 'gctx>(
             .extend(args);
     }
 
-    if honor_rust_version {
+    if honor_rust_version.unwrap_or(true) {
         let rustc_version = target_data.rustc.version.clone().into();
 
         let mut incompatible = Vec::new();

src/cargo/ops/cargo_install.rs

@@ -624,7 +624,7 @@ pub fn install(
     let dst = root.join("bin").into_path_unlocked();
     let map = SourceConfigMap::new(gctx)?;
 
-    let current_rust_version = if opts.honor_rust_version {
+    let current_rust_version = if opts.honor_rust_version.unwrap_or(true) {
         let rustc = gctx.load_global_rustc(None)?;
         Some(rustc.version.clone().into())
     } else {

src/cargo/ops/cargo_package.rs

@@ -933,7 +933,7 @@ fn run_verify(
             target_rustc_args: rustc_args,
             target_rustc_crate_types: None,
             rustdoc_document_private_items: false,
-            honor_rust_version: true,
+            honor_rust_version: None,
         },
         &exec,
     )?;

src/cargo/util/command_prelude.rs

@@ -534,6 +534,10 @@ pub trait ArgMatchesExt {
         self.maybe_flag("keep-going")
     }
 
+    fn honor_rust_version(&self) -> Option<bool> {
+        self.flag("ignore-rust-version").then_some(false)
+    }
+
     fn targets(&self) -> CargoResult<Vec<String>> {
         if self.is_present_with_zero_values("target") {
             let cmd = if is_rustup() {
@@ -763,7 +767,7 @@ Run `{cmd}` to see possible targets."
             target_rustc_args: None,
             target_rustc_crate_types: None,
             rustdoc_document_private_items: false,
-            honor_rust_version: !self.flag("ignore-rust-version"),
+            honor_rust_version: self.honor_rust_version(),
         };
 
         if let Some(ws) = workspace {