enhancement: Enhance Enum types with string conversion capabilities

For certain enum types, we need to convert them to their corresponding
strings, or be able to map a given string to the corresponding enum type.
However, many enum types currently lack these helper functions. With the
help with strum macro, we can easily reach this goal. But we also take
some special cases which are partially implemented into account. For these,
myabe we just implement `impl std::fmt::Display` for it.

Fixes #173

Signed-off-by: Alex Lyn <alex.lyn@antgroup.com>

Cargo.toml

@@ -30,6 +30,8 @@ serde_json = "1.0.66"
 quickcheck = { version = "1.0.3", optional = true }
 derive_builder = "0.20.0"
 getset = "0.1.1"
+strum = "0.26.2"
+strum_macros = "0.26.2"
 
 [dev-dependencies]
 tempfile = "3.2.0"

src/distribution/error.rs

@@ -5,13 +5,15 @@ use derive_builder::Builder;
 use getset::Getters;
 use serde::{Deserialize, Serialize};
 use std::fmt::{self, Display, Formatter};
+use strum_macros::{Display as StrumDisplay, EnumString};
 use thiserror::Error;
 
 /// The string returned by and ErrorResponse error.
 pub const ERR_REGISTRY: &str = "distribution: registry returned error";
 
 /// Unique identifier representing error code.
-#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize, StrumDisplay, EnumString)]
+#[strum(serialize_all = "SCREAMING_SNAKE_CASE")]
 #[serde(rename_all = "SCREAMING_SNAKE_CASE")]
 pub enum ErrorCode {
     /// Blob unknown to registry.

src/runtime/capability.rs

@@ -4,10 +4,12 @@ use serde::{
 };
 use std::collections::HashSet;
 
+use strum_macros::{Display, EnumString};
+
 /// Capabilities is a unique set of Capability values.
 pub type Capabilities = HashSet<Capability>;
 
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, Serialize)]
+#[derive(Clone, Copy, Debug, EnumString, Eq, Display, Hash, PartialEq, Serialize)]
 /// All available capabilities.
 ///
 /// For the purpose of performing permission checks, traditional UNIX
@@ -21,6 +23,7 @@ pub type Capabilities = HashSet<Capability>;
 /// Starting with kernel 2.2, Linux divides the privileges traditionally
 /// associated with superuser into distinct units, known as capabilities, which
 /// can be independently enabled and disabled. Capabilities are a per-thread attribute.
+#[strum(serialize_all = "SCREAMING_SNAKE_CASE")]
 pub enum Capability {
     #[serde(rename = "CAP_AUDIT_CONTROL")]
     /// Enable and disable kernel auditing; change auditing filter rules;
@@ -609,4 +612,60 @@ mod tests {
         assert!(res.contains(&Capability::Chown));
         Ok(())
     }
+
+    #[test]
+    fn invalid_string2enum() {
+        let invalid_cap_str = "INVALID_CAP";
+        let unknown_cap = invalid_cap_str.parse::<Capability>();
+        assert!(unknown_cap.is_err());
+    }
+
+    #[test]
+    fn cap_enum_to_string() {
+        let cap = Capability::AuditControl;
+        assert_eq!(cap.to_string(), "AUDIT_CONTROL");
+
+        let cap = Capability::AuditRead;
+        assert_eq!(cap.to_string(), "AUDIT_READ");
+
+        let cap = Capability::SysAdmin;
+        assert_eq!(cap.to_string(), "SYS_ADMIN");
+    }
+
+    #[test]
+    fn cap_string_to_enum() {
+        let cap_str = "AUDIT_CONTROL";
+        let cap_enum: Capability = cap_str.parse().unwrap();
+        assert_eq!(cap_enum, Capability::AuditControl);
+
+        let cap_str = "AUDIT_READ";
+        let cap_enum: Capability = cap_str.parse().unwrap();
+        assert_eq!(cap_enum, Capability::AuditRead);
+
+        let cap_str = "SYS_ADMIN";
+        let cap_enum: Capability = cap_str.parse().unwrap();
+        assert_eq!(cap_enum, Capability::SysAdmin);
+    }
+
+    #[test]
+    fn test_serde_serialization() {
+        let cap = Capability::AuditControl;
+        let serialized = serde_json::to_string(&cap).unwrap();
+        assert_eq!(serialized, "\"CAP_AUDIT_CONTROL\"");
+
+        let cap = Capability::SysAdmin;
+        let serialized = serde_json::to_string(&cap).unwrap();
+        assert_eq!(serialized, "\"CAP_SYS_ADMIN\"");
+    }
+
+    #[test]
+    fn test_serde_deserialization() {
+        let serialized = "\"CAP_AUDIT_CONTROL\"";
+        let cap: Capability = serde_json::from_str(serialized).unwrap();
+        assert_eq!(cap, Capability::AuditControl);
+
+        let serialized = "\"CAP_SYS_ADMIN\"";
+        let cap: Capability = serde_json::from_str(serialized).unwrap();
+        assert_eq!(cap, Capability::SysAdmin);
+    }
 }