impl(generator): Rust uses strings for enum values (#88)

We decided to use strings for enum values, as the transport will be HTTP +
JSON. The generator creates some helper constants in a properly named module,
that prevents typos.

generator/internal/genclient/language/internal/rust/rust.go

@@ -163,16 +163,14 @@ func (c *Codec) FQEnumName(e *genclient.Enum, _ *genclient.APIState) string {
 	return c.messageScopeName(e.Parent) + "::" + c.ToPascal(e.Name)
 }
 
-func (c *Codec) EnumValueName(e *genclient.EnumValue, state *genclient.APIState) string {
-	if e.Parent.Parent != nil {
-		return c.MessageName(e.Parent.Parent, state) + "_" + strcase.ToCamel(e.Name)
-	}
-	return c.ToPascal(e.Name)
+func (c *Codec) EnumValueName(e *genclient.EnumValue, _ *genclient.APIState) string {
+	// The Protobuf naming convention is to use SCREAMING_SNAKE_CASE, we do not
+	// need to change anything for Rust
+	return EscapeKeyword(e.Name)
 }
 
-func (c *Codec) FQEnumValueName(v *genclient.EnumValue, _ *genclient.APIState) string {
-	// TODO(#76) - these will be `const` strings and therefore should be SNAKE_UPPERCASE.
-	return c.enumScopeName(v.Parent) + "::" + c.ToSnake(v.Name)
+func (c *Codec) FQEnumValueName(v *genclient.EnumValue, state *genclient.APIState) string {
+	return fmt.Sprintf("%s::%s::%s", c.enumScopeName(v.Parent), c.ToSnake(v.Parent.Name), c.EnumValueName(v, state))
 }
 
 func (c *Codec) BodyAccessor(m *genclient.Method, state *genclient.APIState) string {

generator/internal/genclient/templatedata.go

@@ -249,6 +249,10 @@ func (e *enum) Name() string {
 	return e.c.EnumName(e.s, e.state)
 }
 
+func (e *enum) NameSnakeCase() string {
+	return e.c.ToSnake(e.c.EnumName(e.s, e.state))
+}
+
 func (e *enum) DocLines() []string {
 	ss := strings.Split(e.s.Documentation, "\n")
 	for i := range ss {

generator/templates/rust/enum.mustache

@@ -1,13 +1,16 @@
-
+{{#DocLines}}
+/// {{{.}}}
+{{/DocLines}}
 #[derive(Clone, Debug, Default, Deserialize, Serialize)]
-pub struct {{Name}}(i32);
+pub struct {{Name}}(String);
 
-impl {{Name}} {
+/// Useful constants to work with [{{Name}}]({{Name}})
+pub mod {{NameSnakeCase}} {
     {{#Values}}
 
     {{#DocLines}}
     /// {{{.}}}
     {{/DocLines}}
-    pub const {{Name}}: {{EnumType}} = {{EnumType}}({{Number}});
+    pub const {{Name}}: &str = "{{Name}}";
     {{/Values}}
-}
+}

generator/testdata/rust/gclient/golden/model.rs

@@ -174,31 +174,35 @@ pub struct SecretVersion {
 
 /// Defines additional types related to SecretVersion
 pub mod secret_version {
-
+    /// The state of a
+    /// [SecretVersion][google.cloud.secretmanager.v1.SecretVersion], indicating if
+    /// it can be accessed.
     #[derive(Clone, Debug, Default, Deserialize, Serialize)]
-    pub struct State(i32);
+    pub struct State(String);
 
-    impl State {
+    /// Useful constants to work with [State](State)
+    pub mod state {
 
         /// Not specified. This value is unused and invalid.
-        pub const SecretVersion_StateUnspecified: State = State(0);
+        pub const STATE_UNSPECIFIED: &str = "STATE_UNSPECIFIED";
 
         /// The [SecretVersion][google.cloud.secretmanager.v1.SecretVersion] may be
         /// accessed.
-        pub const SecretVersion_Enabled: State = State(1);
+        pub const ENABLED: &str = "ENABLED";
 
         /// The [SecretVersion][google.cloud.secretmanager.v1.SecretVersion] may not
         /// be accessed, but the secret data is still available and can be placed
         /// back into the
         /// [ENABLED][google.cloud.secretmanager.v1.SecretVersion.State.ENABLED]
         /// state.
-        pub const SecretVersion_Disabled: State = State(2);
+        pub const DISABLED: &str = "DISABLED";
 
         /// The [SecretVersion][google.cloud.secretmanager.v1.SecretVersion] is
         /// destroyed and the secret data is no longer stored. A version may not
         /// leave this state once entered.
-        pub const SecretVersion_Destroyed: State = State(3);
-    }}
+        pub const DESTROYED: &str = "DESTROYED";
+    }
+}
 
 /// A policy that defines the replication and encryption configuration of data.
 #[derive(Clone, Debug, Default, Deserialize, Serialize)]