refactor!: use parse-display instead of serde

To ensure enum string representations are consistent with their variant
names we want to derive the string handling (`Display`/`FromStr`). We've
so far used the somewhat convoluted approach of deriving
`serde::{Deserialize, Serialize}` and using `serde_plain`'s proc macros
to generate implementations of `Display` and `FromStr` that forward to
`serde`, but this puts quite a lot in the public API for each enum that
we don't really want:

- `serde::Deserialize`
- `serde::Serialize`
- `serde_plain::Error`

`parse-display` is another derive macro the specifically generates a
`Display` and corresponding `FromStr` implementation. It still leaks an
error type into the API but this is only one thing instead of 3.

BREAKING CHANGE: `Capability`, `ChangeSetStatus`, `ResourceStatus`,
`StackStatus`, `change_set::Evaluation`, `change_set::ExecutionStatus`,
`change_set::ModifyScope`, `change_set::Replacement`, and
`change_set::RequiresRecreation` no longer implement `serde::{Deserialize,
Serialize}`, and their `FromStr` implementations now use
`parse_display::ParseError` as the `Err` type.

Cargo.toml

@@ -14,14 +14,13 @@ aws-sdk-cloudformation = "0.19.0"
 aws-sdk-sts = "0.19.0"
 aws-smithy-types-convert = { version = "0.49.0", features = ["convert-chrono"] }
 chrono = "0.4.19"
-enumset = { version = "1.0.6", features = ["serde"] }
+enumset = "1.0.6"
 futures-util = "0.3.14"
 lazy_static = "1.4.0"
+parse-display = { version = "0.6.0", default-features = false }
 regex = "1.5.4"
-serde = { version = "1.0.125", features = ["derive"] }
 serde_json = "1.0.85"
-serde_plain = "0.3.0"
-tokio = { version = "1.4.0" }
+tokio = "1.4.0"
 
 [dev-dependencies]
 assert_matches = "1.5.0"

src/apply_stack.rs

@@ -9,7 +9,6 @@ use aws_sdk_cloudformation::{
 use aws_smithy_types_convert::date_time::DateTimeExt;
 use chrono::{DateTime, Utc};
 use futures_util::{Stream, TryFutureExt, TryStreamExt};
-use serde_plain::{forward_display_to_serde, forward_from_str_to_serde};
 
 use crate::{
     change_set::{
@@ -316,18 +315,18 @@ impl ApplyStackInput {
 /// [2]: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-macros.html
 /// [`AWS::Include`]: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/create-reusable-transform-function-snippets-and-add-to-your-template-with-aws-include-transform.html
 /// [`AWS::Serverless`]: http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/transform-aws-serverless.html
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
 pub enum Capability {
     /// Acknowledge IAM resources (*without* custom names only).
-    #[serde(rename = "CAPABILITY_IAM")]
+    #[display("CAPABILITY_IAM")]
     Iam,
 
     /// Acknowledge IAM resources (with or without custom names).
-    #[serde(rename = "CAPABILITY_NAMED_IAM")]
+    #[display("CAPABILITY_NAMED_IAM")]
     NamedIam,
 
     /// Acknowledge macro expansion.
-    #[serde(rename = "CAPABILITY_AUTO_EXPAND")]
+    #[display("CAPABILITY_AUTO_EXPAND")]
     AutoExpand,
 }
 
@@ -341,9 +340,6 @@ impl Capability {
     }
 }
 
-forward_display_to_serde!(Capability);
-forward_from_str_to_serde!(Capability);
-
 /// An input parameter for an `apply_stack` operation.
 ///
 /// Note that, unlike when directly updating a stack, it is not possible to reuse previous
@@ -856,3 +852,24 @@ async fn describe_output(
         .expect("DescribeStacksOutput empty stacks");
     Ok(ApplyStackOutput::from_raw(stack))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Capability;
+
+    #[test]
+    fn test_parse_display() {
+        assert_eq!(Capability::Iam.to_string(), "CAPABILITY_IAM");
+        assert_eq!(Capability::Iam, "CAPABILITY_IAM".parse().unwrap());
+        assert_eq!(Capability::NamedIam.to_string(), "CAPABILITY_NAMED_IAM");
+        assert_eq!(
+            Capability::NamedIam,
+            "CAPABILITY_NAMED_IAM".parse().unwrap(),
+        );
+        assert_eq!(Capability::AutoExpand.to_string(), "CAPABILITY_AUTO_EXPAND");
+        assert_eq!(
+            Capability::AutoExpand,
+            "CAPABILITY_AUTO_EXPAND".parse().unwrap(),
+        );
+    }
+}

src/change_set.rs

@@ -13,7 +13,6 @@ use aws_smithy_types_convert::date_time::DateTimeExt;
 use chrono::{DateTime, Utc};
 use enumset::EnumSet;
 use futures_util::TryFutureExt;
-use serde_plain::{forward_display_to_serde, forward_from_str_to_serde};
 use tokio::time::{interval_at, Instant};
 
 use crate::{
@@ -179,8 +178,8 @@ impl ChangeSet {
 }
 
 /// The change set's execution status.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
-#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
+#[display(style = "SNAKE_CASE")]
 pub enum ExecutionStatus {
     /// The change set is not available to execute.
     Unavailable,
@@ -201,9 +200,6 @@ pub enum ExecutionStatus {
     Obsolete,
 }
 
-forward_display_to_serde!(ExecutionStatus);
-forward_from_str_to_serde!(ExecutionStatus);
-
 /// A parameter set for a change set.
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Parameter {
@@ -420,7 +416,7 @@ impl ModifyDetail {
 /// [`Never`]: RequiresRecreation::Never
 /// [`Static`]: Evaluation::Static
 /// [`Dynamic`]: Evaluation::Dynamic
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
 pub enum Replacement {
     /// The resource will be replaced.
     True,
@@ -432,18 +428,15 @@ pub enum Replacement {
     Conditional,
 }
 
-forward_display_to_serde!(Replacement);
-forward_from_str_to_serde!(Replacement);
-
 // The derive for EnumSetType creates an item that triggers this lint, so it has to be disabled
 // at the module level. We don't want to disable it too broadly though, so we wrap its declaration
 // in a module and re-export from that.
 mod modify_scope {
     #![allow(clippy::expl_impl_clone_on_copy)]
 
     /// Indicates which resource attribute is triggering this update.
-    #[derive(Debug, enumset::EnumSetType, serde::Deserialize, serde::Serialize)]
-    #[enumset(no_ops, serialize_as_list)]
+    #[derive(Debug, enumset::EnumSetType, parse_display::Display, parse_display::FromStr)]
+    #[enumset(no_ops)]
     pub enum ModifyScope {
         /// A change to the resource's properties.
         Properties,
@@ -466,9 +459,6 @@ mod modify_scope {
 }
 pub use modify_scope::ModifyScope;
 
-forward_display_to_serde!(ModifyScope);
-forward_from_str_to_serde!(ModifyScope);
-
 /// A change that AWS CloudFormation will make to a resource.
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct ResourceChangeDetail {
@@ -592,7 +582,7 @@ impl ChangeSource {
     }
 }
 
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
 pub enum Evaluation {
     /// AWS CloudFormation can determine that the target value will change, and its value.
     ///
@@ -611,9 +601,6 @@ pub enum Evaluation {
     Dynamic,
 }
 
-forward_display_to_serde!(Evaluation);
-forward_from_str_to_serde!(Evaluation);
-
 /// The field that AWS CloudFormation will change, such as the name of a resource's property, and
 /// whether the resource will be recreated.
 #[derive(Clone, Debug, Eq, PartialEq)]
@@ -703,7 +690,7 @@ impl ResourceTargetDefinition {
 }
 
 /// Indicates whether a change to a property causes the resource to be recreated.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
 pub enum RequiresRecreation {
     /// The resource will not need to be recreated.
     Never,
@@ -718,9 +705,6 @@ pub enum RequiresRecreation {
     Always,
 }
 
-forward_display_to_serde!(RequiresRecreation);
-forward_from_str_to_serde!(RequiresRecreation);
-
 pub(crate) struct ChangeSetWithType {
     pub(crate) change_set: ChangeSet,
     pub(crate) change_set_type: ChangeSetType,

src/lib.rs

@@ -19,9 +19,7 @@ pub use apply_stack::{
 pub use delete_stack::{DeleteStack, DeleteStackError, DeleteStackEvents, DeleteStackInput};
 pub use event::{StackEvent, StackEventDetails};
 pub use stack::{StackFailure, StackWarning};
-pub use status::{
-    ChangeSetStatus, InvalidStatus, ResourceStatus, StackStatus, Status, StatusSentiment,
-};
+pub use status::{ChangeSetStatus, ResourceStatus, StackStatus, Status, StatusSentiment};
 pub use tag::Tag;
 
 /// A client for performing cloudformatious operations.

src/status.rs

@@ -1,10 +1,6 @@
 //! Types and values representing various CloudFormation statuses.
 #![allow(clippy::module_name_repetitions)]
 
-use std::str::FromStr;
-
-use serde_plain::forward_display_to_serde;
-
 /// Common operations for statuses.
 pub trait Status: std::fmt::Debug + std::fmt::Display + private::Sealed {
     /// Indicates whether or not a status is terminal.
@@ -50,13 +46,9 @@ impl StatusSentiment {
     }
 }
 
-/// An error marker returned when trying to parse an invalid status.
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
-pub struct InvalidStatus;
-
 /// Possible change set statuses.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
-#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
+#[display(style = "SNAKE_CASE")]
 pub enum ChangeSetStatus {
     CreatePending,
     CreateInProgress,
@@ -91,19 +83,9 @@ impl Status for ChangeSetStatus {
     }
 }
 
-forward_display_to_serde!(ChangeSetStatus);
-
-impl FromStr for ChangeSetStatus {
-    type Err = InvalidStatus;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        serde_plain::from_str(s).map_err(|_| InvalidStatus)
-    }
-}
-
 /// Possible stack statuses.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
-#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
+#[display(style = "SNAKE_CASE")]
 pub enum StackStatus {
     CreateInProgress,
     CreateFailed,
@@ -185,19 +167,9 @@ impl Status for StackStatus {
     }
 }
 
-forward_display_to_serde!(StackStatus);
-
-impl FromStr for StackStatus {
-    type Err = InvalidStatus;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        serde_plain::from_str(s).map_err(|_| InvalidStatus)
-    }
-}
-
 /// Possible resource statuses.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
-#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, parse_display::Display, parse_display::FromStr)]
+#[display(style = "SNAKE_CASE")]
 pub enum ResourceStatus {
     CreateInProgress,
     CreateFailed,
@@ -261,16 +233,6 @@ impl Status for ResourceStatus {
     }
 }
 
-forward_display_to_serde!(ResourceStatus);
-
-impl FromStr for ResourceStatus {
-    type Err = InvalidStatus;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        serde_plain::from_str(s).map_err(|_| InvalidStatus)
-    }
-}
-
 mod private {
     /// An unreachable trait used to prevent some traits from being implemented outside the crate.
     pub trait Sealed {}
@@ -295,7 +257,7 @@ mod tests {
             "UPDATE_ROLLBACK_COMPLETE_CLEANUP_IN_PROGRESS".parse(),
             Ok(StackStatus::UpdateRollbackCompleteCleanupInProgress)
         );
-        assert_eq!("oh no".parse::<StackStatus>(), Err(InvalidStatus));
+        assert!("oh no".parse::<StackStatus>().is_err());
     }
 
     #[test]
@@ -309,6 +271,6 @@ mod tests {
             "IMPORT_ROLLBACK_IN_PROGRESS".parse(),
             Ok(ResourceStatus::ImportRollbackInProgress)
         );
-        assert_eq!("oh no".parse::<ResourceStatus>(), Err(InvalidStatus));
+        assert!("oh no".parse::<ResourceStatus>().is_err());
     }
 }