Represent metadata version as an enum

src/config.rs

@@ -10,6 +10,7 @@ use serde::Deserialize;
 use thiserror::Error as ThisError;
 use tokio_stream::StreamExt;
 
+use crate::settings::MetadataVersion;
 use crate::{
     cli::self_update::SelfUpdateMode,
     currentprocess::process,
@@ -22,7 +23,7 @@ use crate::{
     fallback_settings::FallbackSettings,
     install::UpdateStatus,
     notifications::*,
-    settings::{Settings, SettingsFile, DEFAULT_METADATA_VERSION},
+    settings::{Settings, SettingsFile},
     toolchain::{
         distributable::DistributableToolchain,
         names::{
@@ -459,20 +460,19 @@ impl Cfg {
 
     #[cfg_attr(feature = "otel", tracing::instrument(skip_all))]
     pub(crate) fn upgrade_data(&self) -> Result<()> {
-        let current_version = self.settings_file.with(|s| Ok(s.version.clone()))?;
-
-        if current_version == DEFAULT_METADATA_VERSION {
-            (self.notify_handler)(Notification::MetadataUpgradeNotNeeded(&current_version));
+        let current_version = self.settings_file.with(|s| Ok(s.version))?;
+        if current_version == MetadataVersion::default() {
+            (self.notify_handler)(Notification::MetadataUpgradeNotNeeded(current_version));
             return Ok(());
         }
 
         (self.notify_handler)(Notification::UpgradingMetadata(
-            &current_version,
-            DEFAULT_METADATA_VERSION,
+            current_version,
+            MetadataVersion::default(),
         ));
 
-        match &*current_version {
-            "2" => {
+        match current_version {
+            MetadataVersion::V2 => {
                 // The toolchain installation format changed. Just delete them all.
                 (self.notify_handler)(Notification::UpgradeRemovesToolchains);
 
@@ -490,11 +490,11 @@ impl Cfg {
                 }
 
                 self.settings_file.with_mut(|s| {
-                    DEFAULT_METADATA_VERSION.clone_into(&mut s.version);
+                    s.version = MetadataVersion::default();
                     Ok(())
                 })
             }
-            _ => Err(RustupError::UnknownMetadataVersion(current_version).into()),
+            MetadataVersion::V12 => unreachable!(),
         }
     }
 
@@ -878,8 +878,8 @@ impl Cfg {
         utils::assert_is_directory(&self.rustup_dir)?;
 
         self.settings_file.with(|s| {
-            (self.notify_handler)(Notification::ReadMetadataVersion(&s.version));
-            if s.version == DEFAULT_METADATA_VERSION {
+            (self.notify_handler)(Notification::ReadMetadataVersion(s.version));
+            if s.version == MetadataVersion::default() {
                 Ok(())
             } else {
                 Err(anyhow!(

src/notifications.rs

@@ -1,6 +1,7 @@
 use std::fmt::{self, Display};
 use std::path::{Path, PathBuf};
 
+use crate::settings::MetadataVersion;
 use crate::{
     dist::{dist::ToolchainDesc, temp},
     toolchain::names::ToolchainName,
@@ -26,9 +27,9 @@ pub(crate) enum Notification<'a> {
     UninstallingToolchain(&'a ToolchainName),
     UninstalledToolchain(&'a ToolchainName),
     UpdateHashMatches,
-    UpgradingMetadata(&'a str, &'a str),
-    MetadataUpgradeNotNeeded(&'a str),
-    ReadMetadataVersion(&'a str),
+    UpgradingMetadata(MetadataVersion, MetadataVersion),
+    MetadataUpgradeNotNeeded(MetadataVersion),
+    ReadMetadataVersion(MetadataVersion),
     NonFatalError(&'a anyhow::Error),
     UpgradeRemovesToolchains,
     /// Both `rust-toolchain` and `rust-toolchain.toml` exist within a directory

src/settings.rs

@@ -1,5 +1,6 @@
 use std::cell::RefCell;
 use std::collections::BTreeMap;
+use std::fmt;
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
 
@@ -12,9 +13,6 @@ use crate::notifications::*;
 use crate::utils::toml_utils::*;
 use crate::utils::utils;
 
-pub(crate) const SUPPORTED_METADATA_VERSIONS: [&str; 2] = ["2", "12"];
-pub(crate) const DEFAULT_METADATA_VERSION: &str = "12";
-
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct SettingsFile {
     path: PathBuf,
@@ -78,7 +76,7 @@ impl SettingsFile {
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Settings {
-    pub version: String,
+    pub version: MetadataVersion,
     pub default_host_triple: Option<String>,
     pub default_toolchain: Option<String>,
     pub profile: Option<Profile>,
@@ -90,7 +88,7 @@ pub struct Settings {
 impl Default for Settings {
     fn default() -> Self {
         Self {
-            version: DEFAULT_METADATA_VERSION.to_owned(),
+            version: MetadataVersion::default(),
             default_host_triple: None,
             default_toolchain: None,
             profile: Some(Profile::default()),
@@ -152,9 +150,8 @@ impl Settings {
 
     pub(crate) fn from_toml(mut table: toml::value::Table, path: &str) -> Result<Self> {
         let version = get_string(&mut table, "version", path)?;
-        if !SUPPORTED_METADATA_VERSIONS.contains(&&*version) {
-            return Err(RustupError::UnknownMetadataVersion(version).into());
-        }
+        let version = MetadataVersion::from_str(&version)?;
+
         let auto_self_update = get_opt_string(&mut table, "auto_self_update", path)?
             .and_then(|mode| SelfUpdateMode::from_str(mode.as_str()).ok());
         let profile = get_opt_string(&mut table, "profile", path)?
@@ -172,7 +169,10 @@ impl Settings {
     pub(crate) fn into_toml(self) -> toml::value::Table {
         let mut result = toml::value::Table::new();
 
-        result.insert("version".to_owned(), toml::Value::String(self.version));
+        result.insert(
+            "version".to_owned(),
+            toml::Value::String(self.version.as_str().to_owned()),
+        );
 
         if let Some(v) = self.default_host_triple {
             result.insert("default_host_triple".to_owned(), toml::Value::String(v));
@@ -227,3 +227,37 @@ impl Settings {
         result
     }
 }
+
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
+pub(crate) enum MetadataVersion {
+    V2,
+    #[default]
+    V12,
+}
+
+impl MetadataVersion {
+    fn as_str(&self) -> &'static str {
+        match self {
+            Self::V2 => "2",
+            Self::V12 => "12",
+        }
+    }
+}
+
+impl FromStr for MetadataVersion {
+    type Err = RustupError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "2" => Ok(Self::V2),
+            "12" => Ok(Self::V12),
+            _ => Err(RustupError::UnknownMetadataVersion(s.to_owned())),
+        }
+    }
+}
+
+impl fmt::Display for MetadataVersion {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.as_str())
+    }
+}