fix: repair toolchains missing their installed manifest

src/dist/manifestation.rs

@@ -29,14 +29,13 @@ use crate::{
         config::Config,
         download::{DownloadCfg, DownloadStatus, File},
         manifest::{Component, CompressionKind, HashedBinary, Manifest},
-        prefix::InstallPrefix,
+        prefix::{DIST_MANIFEST, InstallPrefix},
         temp,
     },
     errors::RustupError,
     utils,
 };
 
-pub(crate) const DIST_MANIFEST: &str = "multirust-channel-manifest.toml";
 pub(crate) const CONFIG_FILE: &str = "multirust-config.toml";
 
 #[derive(Debug)]
@@ -396,8 +395,7 @@ impl Manifestation {
     #[tracing::instrument(level = "trace")]
     pub fn load_manifest(&self) -> Result<Option<Manifest>> {
         let prefix = self.installation.prefix();
-        let old_manifest_path = prefix.manifest_file(DIST_MANIFEST);
-        if utils::path_exists(&old_manifest_path) {
+        if let Some(old_manifest_path) = prefix.dist_manifest() {
             let manifest_str = utils::read_file("installed manifest", &old_manifest_path)?;
             Ok(Some(Manifest::parse(&manifest_str).with_context(|| {
                 RustupError::ParsingFile {

src/dist/mod.rs

@@ -1125,10 +1125,9 @@ async fn try_update_from_dist_(
     } else {
         download
             .dl_v2_manifest(
-                // Even if manifest has not changed, we must continue to install requested components.
-                // So if components or targets is not empty, we skip passing `update_hash` so that
-                // we essentially degenerate to `rustup component add` / `rustup target add`
-                if components.is_empty() && targets.is_empty() {
+                // Skip the update hash when the installed manifest is missing or when components
+                // or targets were requested, since either case still requires the channel manifest.
+                if prefix.dist_manifest().is_some() && components.is_empty() && targets.is_empty() {
                     Some(update_hash)
                 } else {
                     None

src/dist/prefix.rs

@@ -11,6 +11,7 @@ const REL_MANIFEST_DIR: &str = match std::path::MAIN_SEPARATOR {
 };
 
 static V1_COMMON_COMPONENT_LIST: &[&str] = &["cargo", "rustc", "rust-docs"];
+pub(crate) const DIST_MANIFEST: &str = "multirust-channel-manifest.toml";
 
 #[derive(Clone, Debug)]
 pub struct InstallPrefix {
@@ -37,6 +38,11 @@ impl InstallPrefix {
         path
     }
 
+    pub(crate) fn dist_manifest(&self) -> Option<PathBuf> {
+        let path = self.manifest_file(DIST_MANIFEST);
+        utils::path_exists(&path).then_some(path)
+    }
+
     pub(crate) fn rel_manifest_file(&self, name: &str) -> PathBuf {
         let mut path = PathBuf::from(REL_MANIFEST_DIR);
         path.push(name);

src/toolchain/distributable.rs

@@ -439,12 +439,14 @@ impl<'a> DistributableToolchain<'a> {
     }
 
     pub async fn fetch_dist_manifest(&self) -> anyhow::Result<Option<ManifestWithHash>> {
+        let prefix = InstallPrefix::from(self.toolchain.path());
+        let update_hash = if prefix.dist_manifest().is_some() {
+            Some(self.toolchain.cfg.get_hash_file(&self.desc, false)?)
+        } else {
+            None
+        };
         DownloadCfg::new(self.toolchain.cfg)
-            .dl_v2_manifest(
-                Some(&self.toolchain.cfg.get_hash_file(&self.desc, false)?),
-                &self.desc,
-                self.toolchain.cfg,
-            )
+            .dl_v2_manifest(update_hash.as_deref(), &self.desc, self.toolchain.cfg)
             .await
     }
 

tests/suite/cli_rustup.rs

@@ -4201,14 +4201,7 @@ async fn missing_manifest_shows_reinstall_help() {
         .await
         .is_ok();
 
-    let manifest_path = cx
-        .config
-        .rustupdir
-        .join("toolchains")
-        .join(format!("nightly-{}", this_host_tuple()))
-        .join("lib")
-        .join("rustlib")
-        .join("multirust-channel-manifest.toml");
+    let manifest_path = nightly_manifest_path(&cx);
 
     fs::remove_file(&manifest_path).unwrap();
 
@@ -4223,3 +4216,51 @@ help: try reinstalling or updating the toolchain
 "#]])
         .is_err();
 }
+
+#[tokio::test]
+async fn reinstall_restores_missing_manifest() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+
+    cx.config
+        .expect(["rustup", "toolchain", "install", "nightly"])
+        .await
+        .is_ok();
+
+    let manifest_path = nightly_manifest_path(&cx);
+
+    fs::remove_file(&manifest_path).unwrap();
+
+    cx.config
+        .expect(["rustup", "toolchain", "install", "nightly"])
+        .await
+        .is_ok();
+
+    assert!(manifest_path.exists());
+}
+
+#[tokio::test]
+async fn update_all_restores_missing_manifest() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+
+    cx.config
+        .expect(["rustup", "toolchain", "install", "nightly"])
+        .await
+        .is_ok();
+
+    let manifest_path = nightly_manifest_path(&cx);
+    fs::remove_file(&manifest_path).unwrap();
+
+    cx.config.expect(["rustup", "update"]).await.is_ok();
+
+    assert!(manifest_path.exists());
+}
+
+fn nightly_manifest_path(cx: &CliTestContext) -> PathBuf {
+    cx.config
+        .rustupdir
+        .join("toolchains")
+        .join(format!("nightly-{}", this_host_tuple()))
+        .join("lib")
+        .join("rustlib")
+        .join("multirust-channel-manifest.toml")
+}