fix(cargo): restore sparse index version discovery

e2e/cli/test_error_display

@@ -49,7 +49,7 @@ local_assert_fail "mise install core:node@invalid-version" \
 # Test 2: Backend error (cargo)
 echo "Test 2: Cargo backend error"
 local_assert_fail "mise install cargo:nonexistent-crate-12345@1.0.0" \
-  "mise ERROR Failed to install cargo:nonexistent-crate-12345@1.0.0: HTTP status client error (404 Not Found) for url (https://crates.io/api/v1/crates/nonexistent-crate-12345/versions)"
+  "mise ERROR Failed to install cargo:nonexistent-crate-12345@1.0.0: HTTP status client error (404 Not Found) for url (https://index.crates.io/no/ne/nonexistent-crate-12345)"
 
 # Test 3: GitHub repository not found
 echo "Test 3: GitHub repository not found"
@@ -89,7 +89,7 @@ local_assert_fail "mise install core:node@invalid-version" \
 # Test 2: Backend error (cargo) - check for error format with full chain
 echo "Test 2: Cargo backend error"
 local_assert_fail "mise install cargo:nonexistent-crate-12345@1.0.0" \
-  "0: Failed to install cargo:nonexistent-crate-12345@1.0.0: HTTP status client error (404 Not Found) for url (https://crates.io/api/v1/crates/nonexistent-crate-12345/versions)"
+  "0: Failed to install cargo:nonexistent-crate-12345@1.0.0: HTTP status client error (404 Not Found) for url (https://index.crates.io/no/ne/nonexistent-crate-12345)"
 
 # Test 3: GitHub repository not found - check for error format with full chain
 echo "Test 3: GitHub repository not found"

src/backend/cargo.rs

@@ -5,6 +5,7 @@ use std::{fmt::Debug, sync::Arc};
 use async_trait::async_trait;
 use color_eyre::Section;
 use eyre::{bail, eyre};
+use serde_json::Deserializer;
 use url::Url;
 
 mod native_binstall;
@@ -157,26 +158,11 @@ impl Backend for CargoBackend {
             }]);
         }
 
-        // Use crates.io API which includes created_at timestamps
-        let url = format!(
-            "https://crates.io/api/v1/crates/{}/versions",
-            self.tool_name()
-        );
-        let response: CratesIoVersionsResponse = HTTP_FETCH.json(&url).await?;
-
-        let versions = response
-            .versions
-            .into_iter()
-            .filter(|v| !v.yanked)
-            .map(|v| VersionInfo {
-                version: v.num,
-                created_at: Some(v.created_at),
-                ..Default::default()
-            })
-            .rev() // API returns newest first, we want oldest first
-            .collect();
+        let response = HTTP_FETCH
+            .get_text(get_crate_url(&self.tool_name())?)
+            .await?;
 
-        Ok(versions)
+        parse_crate_versions(&response)
     }
 
     async fn install_version_(&self, ctx: &InstallContext, tv: ToolVersion) -> Result<ToolVersion> {
@@ -428,16 +414,44 @@ fn format_tool_options(options: &[&'static str]) -> String {
         .join(", ")
 }
 
-#[derive(Debug, serde::Deserialize)]
-struct CratesIoVersionsResponse {
-    versions: Vec<CratesIoVersion>,
+fn get_crate_url(name: &str) -> eyre::Result<Url> {
+    if name.is_empty() || !name.is_ascii() {
+        bail!("invalid Cargo crate name: {name:?}");
+    }
+    let name = name.to_lowercase();
+    let url = match name.len() {
+        1 => format!("https://index.crates.io/1/{name}"),
+        2 => format!("https://index.crates.io/2/{name}"),
+        3 => format!("https://index.crates.io/3/{}/{name}", &name[..1]),
+        _ => format!(
+            "https://index.crates.io/{}/{}/{name}",
+            &name[..2],
+            &name[2..4]
+        ),
+    };
+    Ok(url.parse()?)
+}
+
+fn parse_crate_versions(response: &str) -> eyre::Result<Vec<VersionInfo>> {
+    let mut versions = vec![];
+    for version in Deserializer::from_str(response).into_iter::<CrateVersion>() {
+        let version = version?;
+        if !version.yanked {
+            versions.push(VersionInfo {
+                version: version.vers,
+                created_at: version.pubtime,
+                ..Default::default()
+            });
+        }
+    }
+    Ok(versions)
 }
 
 #[derive(Debug, serde::Deserialize)]
-struct CratesIoVersion {
-    num: String,
+struct CrateVersion {
+    vers: String,
     yanked: bool,
-    created_at: String,
+    pubtime: Option<String>,
 }
 
 #[cfg(test)]
@@ -560,4 +574,50 @@ mod tests {
             vec!["default-features"]
         );
     }
+
+    #[test]
+    fn crate_index_url_uses_sparse_index_layout() {
+        let cases = [
+            ("a", "https://index.crates.io/1/a"),
+            ("Ab", "https://index.crates.io/2/ab"),
+            ("Abc", "https://index.crates.io/3/a/abc"),
+            ("Cargo-Deny", "https://index.crates.io/ca/rg/cargo-deny"),
+        ];
+
+        for (name, expected) in cases {
+            assert_eq!(get_crate_url(name).unwrap().as_str(), expected);
+        }
+    }
+
+    #[test]
+    fn crate_index_url_rejects_empty_name() {
+        let error = get_crate_url("").unwrap_err();
+
+        assert_eq!(error.to_string(), "invalid Cargo crate name: \"\"");
+    }
+
+    #[test]
+    fn crate_index_url_rejects_non_ascii_name() {
+        let error = get_crate_url("aébc").unwrap_err();
+
+        assert_eq!(error.to_string(), "invalid Cargo crate name: \"aébc\"");
+    }
+
+    #[test]
+    fn parse_crate_versions_uses_pubtime_and_skips_yanked_versions() {
+        let response = r#"{"vers":"1.0.0","yanked":false,"pubtime":"2025-01-01T00:00:00Z"}
+{"vers":"1.1.0","yanked":true,"pubtime":"2025-02-01T00:00:00Z"}
+{"vers":"1.2.0","yanked":false}"#;
+
+        let versions = parse_crate_versions(response).unwrap();
+        let versions = versions
+            .iter()
+            .map(|version| (version.version.as_str(), version.created_at.as_deref()))
+            .collect::<Vec<_>>();
+
+        assert_eq!(
+            versions,
+            vec![("1.0.0", Some("2025-01-01T00:00:00Z")), ("1.2.0", None),]
+        );
+    }
 }