Auto merge of #8454 - GabrielMajeri:config-option-enum, r=ehuss

Add support for deserializing enums in config files

Implements `deserialize_enum` functionality to allow config options which are Rust enums.

@ehuss The code currently has some `todo!`s because I'm not sure how the custom `Deserializer` is supposed to do error handling.

Fixes #8450

Author: bors

src/cargo/util/config/de.rs

@@ -195,11 +195,31 @@ impl<'de, 'config> de::Deserializer<'de> for Deserializer<'config> {
         }
     }
 
+    fn deserialize_enum<V>(
+        self,
+        _name: &'static str,
+        _variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: de::Visitor<'de>,
+    {
+        let value = self
+            .config
+            .get_string_priv(&self.key)?
+            .ok_or_else(|| ConfigError::missing(&self.key))?;
+
+        let Value { val, definition } = value;
+        visitor
+            .visit_enum(val.into_deserializer())
+            .map_err(|e: ConfigError| e.with_key_context(&self.key, definition))
+    }
+
     // These aren't really supported, yet.
     serde::forward_to_deserialize_any! {
         f32 f64 char str bytes
         byte_buf unit unit_struct
-        enum identifier ignored_any
+        identifier ignored_any
     }
 }
 

tests/testsuite/config.rs

@@ -1,5 +1,6 @@
 //! Tests for config settings.
 
+use cargo::core::profiles::Strip;
 use cargo::core::{enable_nightly_features, Shell};
 use cargo::util::config::{self, Config, SslVersionConfig, StringList};
 use cargo::util::interning::InternedString;
@@ -1259,3 +1260,42 @@ fn string_list_advanced_env() {
         "error in environment variable `CARGO_KEY3`: expected string, found integer",
     );
 }
+
+#[cargo_test]
+fn parse_enum() {
+    write_config(
+        "\
+[profile.release]
+strip = 'debuginfo'
+",
+    );
+
+    let config = new_config();
+
+    let p: toml::TomlProfile = config.get("profile.release").unwrap();
+    let strip = p.strip.unwrap();
+    assert_eq!(strip, Strip::DebugInfo);
+}
+
+#[cargo_test]
+fn parse_enum_fail() {
+    write_config(
+        "\
+[profile.release]
+strip = 'invalid'
+",
+    );
+
+    let config = new_config();
+
+    assert_error(
+        config
+            .get::<toml::TomlProfile>("profile.release")
+            .unwrap_err(),
+        "\
+error in [..]/.cargo/config: could not load config key `profile.release.strip`
+
+Caused by:
+  unknown variant `invalid`, expected one of `debuginfo`, `none`, `symbols`",
+    );
+}