fix(upgrade): Improve config error messages

src/errors.rs

@@ -78,10 +78,6 @@ pub(crate) fn non_existent_dependency_err(name: impl Display, table: impl Displa
     )
 }
 
-pub(crate) fn invalid_cargo_config() -> Error {
-    anyhow::format_err!("Invalid cargo config")
-}
-
 pub(crate) fn unsupported_version_req(req: impl Display) -> Error {
     anyhow::format_err!("Support for modifying {} is currently unsupported", req)
 }

src/registry.rs

@@ -13,9 +13,11 @@ pub fn registry_url(manifest_path: &Path, registry: Option<&str>) -> CargoResult
         registries: &mut HashMap<String, Source>,
         path: impl AsRef<Path>,
     ) -> CargoResult<()> {
+        let path = path.as_ref();
         // TODO unit test for source replacement
         let content = std::fs::read_to_string(path)?;
-        let config = toml::from_str::<CargoConfig>(&content).map_err(|_| invalid_cargo_config())?;
+        let config = toml::from_str::<CargoConfig>(&content)
+            .with_context(|| anyhow::format_err!("invalid cargo config at {}", path.display()))?;
         for (key, value) in config.registries {
             registries.entry(key).or_insert(Source {
                 registry: value.index,
@@ -89,8 +91,9 @@ pub fn registry_url(manifest_path: &Path, registry: Option<&str>) -> CargoResult
 
     let registry_url = source
         .registry
-        .and_then(|x| Url::parse(&x).ok())
-        .with_context(invalid_cargo_config)?;
+        .ok_or_else(|| anyhow::format_err!("missing `registry`"))?;
+    let registry_url = Url::parse(&registry_url)
+        .with_context(|| anyhow::format_err!("invalid `registry` field"))?;
 
     Ok(registry_url)
 }