Add extern_enums arg to macros

The `extern_enums` arg is forwarded to the `graphql-client` crate, which
will use it as the type for the enum instead of generating code for it.

By default, the 3 large enums from Function APIs are passed as
`extern_enums`: LanguageCode, CountryCode, CurrencyCode. Users can
override that by sending `extern_enums` explicitly.

Author: jbourassa

example_with_targets/README.md

@@ -76,20 +76,28 @@ input_query = "b.graphql"
 export = "function_b"
 ```
 
-- `target`: the API-specific handle for the target implemented by the Wasm function
-- `input_query`: the path to the target-specific input query file
-- `export` (optional): the name of the Wasm function export to run
-  - default: the target handle as `snake_case`
+- `target`: The API-specific handle for the target implemented by the Wasm function.
+- `input_query`: The path to the target-specific input query file.
+- `export` (optional): The name of the Wasm function export to run.
+  - default: The target handle as `snake_case`.
 
 ## `shopify_function_target` usage
 
 ### Arguments
 
-- `query_path`: the path to the input query file for the target
-- `schema_path`: the path to the API schema file for the target
-- `target` (optional): the API-specific handle for the target if the function name does not match the target handle as `snake_case`
-- `module_name` (optional): the name of the generated module
-  - default: the target handle as `snake_case`
+- `query_path`: A path to a GraphQL query, whose result will be used
+  as the input for the function invocation. The query MUST be named "Input".
+- `schema_path`: A path to Shopify's GraphQL schema definition. You
+  can find it in the `example` folder of the repo, or use the CLI
+  to download a fresh copy (not implemented yet).
+- `target` (optional): The API-specific handle for the target if the function name does not match the target handle as `snake_case`.
+- `module_name` (optional): The name of the generated module.
+  - default: The target handle as `snake_case`
+- `extern_enums` (optional): A list of Enums for which an external type should be used.
+  For those, code generation will be skipped. This is useful for large enums
+  which can increase binary size, or to enums between multiple targets.
+  Example: `extern_enums = ["LanguageCode"]`
+    - default: `["LanguageCode", "CountryCode", "CurrencyCode"]`
 
 ### `src/lib.rs`
 

shopify_function/src/enums.rs

@@ -0,0 +1,3 @@
+pub type CountryCode = String;
+pub type CurrencyCode = String;
+pub type LanguageCode = String;

shopify_function/src/lib.rs

@@ -18,11 +18,14 @@
 
 pub use shopify_function_macro::{generate_types, shopify_function, shopify_function_target};
 
+#[doc(hidden)]
+pub mod enums;
 /// Only used for struct generation.
 #[doc(hidden)]
 pub mod scalars;
 
 pub mod prelude {
+    pub use crate::enums::*;
     pub use crate::scalars::*;
     pub use shopify_function_macro::{generate_types, shopify_function, shopify_function_target};
 }

shopify_function/tests/fixtures/input.graphql

@@ -2,4 +2,5 @@ query Input {
   id
   num
   name
+  country
 }

shopify_function/tests/fixtures/schema.graphql

@@ -28,6 +28,7 @@ type Input {
   id: ID!
   num: Int
   name: String
+  country: CountryCode
 }
 
 """
@@ -51,3 +52,8 @@ The result of the function.
 input FunctionResult {
   name: String
 }
+
+enum CountryCode {
+  AC
+  CA
+}

shopify_function/tests/fixtures/schema_with_targets.graphql

@@ -28,6 +28,7 @@ type Input {
   id: ID!
   num: Int
   name: String
+  country: CountryCode,
   targetAResult: Int @restrictTarget(only: ["test.target-b"])
 }
 
@@ -69,3 +70,8 @@ The result of API target B.
 input FunctionTargetBResult {
   name: String
 }
+
+enum CountryCode {
+  AC
+  CA
+}

shopify_function/tests/shopify_function.rs

@@ -4,7 +4,8 @@ use shopify_function::Result;
 const FUNCTION_INPUT: &str = r#"{
   "id": "gid://shopify/Order/1234567890",
   "num": 123,
-  "name": "test"
+  "name": "test",
+  "country": "CA"
 }"#;
 static mut FUNCTION_OUTPUT: Vec<u8> = vec![];
 

shopify_function/tests/shopify_function_target.rs

@@ -4,7 +4,8 @@ use shopify_function::Result;
 const TARGET_A_INPUT: &str = r#"{
   "id": "gid://shopify/Order/1234567890",
   "num": 123,
-  "name": "test"
+  "name": "test",
+  "country": "CA"
 }"#;
 static mut TARGET_A_OUTPUT: Vec<u8> = vec![];
 
@@ -24,8 +25,11 @@ fn test_target_a_export() {
   output_stream = unsafe { &mut TARGET_A_OUTPUT }
 )]
 fn target_a(
-    _input: target_a::input::ResponseData,
+    input: target_a::input::ResponseData,
 ) -> Result<target_a::output::FunctionTargetAResult> {
+    if input.country != Some("CA".to_string()) {
+        panic!("Expected CountryCode to be a the CA String")
+    }
     Ok(target_a::output::FunctionTargetAResult { status: Some(200) })
 }
 
@@ -49,7 +53,7 @@ fn test_mod_b_export() {
   query_path = "./tests/fixtures/b.graphql",
   schema_path = "./tests/fixtures/schema_with_targets.graphql",
   input_stream = std::io::Cursor::new(TARGET_B_INPUT.as_bytes().to_vec()),
-  output_stream = unsafe { &mut TARGET_B_OUTPUT }
+  output_stream = unsafe { &mut TARGET_B_OUTPUT },
 )]
 fn some_function(
     input: mod_b::input::ResponseData,
@@ -58,3 +62,26 @@ fn some_function(
         name: Some(format!("new name: {}", input.id)),
     })
 }
+
+// Verify that the CountryCode enum is generated when `extern_enums = []`
+#[shopify_function_target(
+  target = "test.target-a",
+  module_name = "country_enum",
+  query_path = "./tests/fixtures/input.graphql",
+  schema_path = "./tests/fixtures/schema_with_targets.graphql",
+  extern_enums = []
+)]
+fn _with_generated_country_code(
+    input: country_enum::input::ResponseData,
+) -> Result<country_enum::output::FunctionTargetAResult> {
+    use country_enum::*;
+
+    let status = match input.country {
+        Some(input::CountryCode::CA) => 200,
+        _ => 201,
+    };
+
+    Ok(output::FunctionTargetAResult {
+        status: Some(status),
+    })
+}

shopify_function_macro/src/lib.rs

@@ -4,7 +4,10 @@ use std::path::Path;
 
 use proc_macro2::{Ident, Span, TokenStream};
 use quote::{quote, ToTokens};
-use syn::{self, parse::Parse, parse::ParseStream, parse_macro_input, Expr, FnArg, LitStr, Token};
+use syn::{
+    self, parse::Parse, parse::ParseStream, parse_macro_input, Expr, ExprArray, FnArg, LitStr,
+    Token,
+};
 
 #[derive(Clone, Default)]
 struct ShopifyFunctionArgs {
@@ -123,6 +126,7 @@ struct ShopifyFunctionTargetArgs {
     schema_path: Option<LitStr>,
     input_stream: Option<Expr>,
     output_stream: Option<Expr>,
+    extern_enums: Option<ExprArray>,
 }
 
 impl ShopifyFunctionTargetArgs {
@@ -156,6 +160,8 @@ impl Parse for ShopifyFunctionTargetArgs {
                 args.input_stream = Some(Self::parse::<kw::input_stream, Expr>(&input)?);
             } else if lookahead.peek(kw::output_stream) {
                 args.output_stream = Some(Self::parse::<kw::output_stream, Expr>(&input)?);
+            } else if lookahead.peek(kw::extern_enums) {
+                args.extern_enums = Some(Self::parse::<kw::extern_enums, ExprArray>(&input)?);
             } else {
                 return Err(lookahead.error());
             }
@@ -170,6 +176,7 @@ struct GenerateTypeArgs {
     schema_path: Option<LitStr>,
     input_stream: Option<Expr>,
     output_stream: Option<Expr>,
+    extern_enums: Option<ExprArray>,
 }
 
 impl GenerateTypeArgs {
@@ -199,6 +206,8 @@ impl Parse for GenerateTypeArgs {
                 args.input_stream = Some(Self::parse::<kw::input_stream, Expr>(&input)?);
             } else if lookahead.peek(kw::output_stream) {
                 args.output_stream = Some(Self::parse::<kw::output_stream, Expr>(&input)?);
+            } else if lookahead.peek(kw::extern_enums) {
+                args.extern_enums = Some(Self::parse::<kw::extern_enums, ExprArray>(&input)?);
             } else {
                 return Err(lookahead.error());
             }
@@ -256,6 +265,27 @@ fn extract_shopify_function_return_type(ast: &syn::ItemFn) -> Result<&syn::Ident
     Ok(&path.path.segments.last().as_ref().unwrap().ident)
 }
 
+/// Generates code for a Function using an explicitly-named target. This will:
+/// - Generate a module to host the generated types.
+/// - Generate types based on the GraphQL schema for the Function input and output.
+/// - Define a wrapper function that's exported to Wasm. The wrapper handles
+///   decoding the input from STDIN, and encoding the output to STDOUT.
+///
+///
+/// The macro takes the following parameters:
+/// - `query_path`: A path to a GraphQL query, whose result will be used
+///    as the input for the function invocation. The query MUST be named "Input".
+/// - `schema_path`: A path to Shopify's GraphQL schema definition. You
+///   can find it in the `example` folder of the repo, or use the CLI
+///   to download a fresh copy.
+/// - `target` (optional): The API-specific handle for the target if the function name does not match the target handle as `snake_case`
+/// - `module_name` (optional): The name of the generated module.
+///   - default: The target handle as `snake_case`
+/// - `extern_enums` (optional): A list of enums for which an external type should be used.
+///   For those, code generation will be skipped. This is useful to skip
+///   codegen for large enums, or share enums between multiple functions.
+///   Example: `extern_enums = ["LanguageCode"]`
+///     - default: `["LanguageCode", "CountryCode", "CurrencyCode"]`
 #[proc_macro_attribute]
 pub fn shopify_function_target(
     attr: proc_macro::TokenStream,
@@ -282,17 +312,21 @@ pub fn shopify_function_target(
 
     let query_path = args.query_path.expect("No value given for query_path");
     let schema_path = args.schema_path.expect("No value given for schema_path");
+    let extern_enums = args.extern_enums.as_ref().map(extract_extern_enums);
     let output_query_file_name = format!(".{}{}", &target_handle_string, OUTPUT_QUERY_FILE_NAME);
 
     let input_struct = generate_struct(
         "Input",
         query_path.value().as_str(),
         schema_path.value().as_str(),
+        extern_enums.as_deref(),
     );
+
     let output_struct = generate_struct(
         "Output",
         &output_query_file_name,
         schema_path.value().as_str(),
+        extern_enums.as_deref(),
     );
     if let Err(error) = extract_shopify_function_return_type(&ast) {
         return error.to_compile_error().into();
@@ -353,12 +387,17 @@ const OUTPUT_QUERY_FILE_NAME: &str = ".output.graphql";
 /// modules generate Rust types from the GraphQL schema file for the Function input
 /// and output respectively.
 ///
-/// The macro takes two parameters:
+/// The macro takes the following parameters:
 /// - `query_path`: A path to a GraphQL query, whose result will be used
 ///    as the input for the function invocation. The query MUST be named "Input".
 /// - `schema_path`: A path to Shopify's GraphQL schema definition. You
 ///   can find it in the `example` folder of the repo, or use the CLI
-///   to download a fresh copy (not implemented yet).
+///   to download a fresh copy.
+/// - `extern_enums`: An list of enums for which an external type should be used.
+///   For those, code generation will be skipped. This is useful to skip
+///   codegen for large enums, or share enums between multiple functions.
+///   Example: `extern_enums = ["LanguageCode"]`
+///   Defaults to: `["LanguageCode", "CountryCode", "CurrencyCode"]`
 ///
 /// Note: This macro creates a file called `.output.graphql` in the root
 /// directory of the project. It can be safely added to your `.gitignore`. We
@@ -375,9 +414,19 @@ pub fn generate_types(attr: proc_macro::TokenStream) -> proc_macro::TokenStream
         .schema_path
         .expect("No value given for schema_path")
         .value();
-
-    let input_struct = generate_struct("Input", query_path.as_str(), schema_path.as_str());
-    let output_struct = generate_struct("Output", OUTPUT_QUERY_FILE_NAME, schema_path.as_str());
+    let extern_enums = args.extern_enums.as_ref().map(extract_extern_enums);
+    let input_struct = generate_struct(
+        "Input",
+        query_path.as_str(),
+        schema_path.as_str(),
+        extern_enums.as_deref(),
+    );
+    let output_struct = generate_struct(
+        "Output",
+        OUTPUT_QUERY_FILE_NAME,
+        schema_path.as_str(),
+        extern_enums.as_deref(),
+    );
     let output_query =
         "mutation Output($result: FunctionResult!) {\n    handleResult(result: $result)\n}\n";
 
@@ -390,16 +439,28 @@ pub fn generate_types(attr: proc_macro::TokenStream) -> proc_macro::TokenStream
     .into()
 }
 
-fn generate_struct(name: &str, query_path: &str, schema_path: &str) -> TokenStream {
+const DEFAULT_EXTERN_ENUMS: &[&str] = &["LanguageCode", "CountryCode", "CurrencyCode"];
+
+fn generate_struct(
+    name: &str,
+    query_path: &str,
+    schema_path: &str,
+    extern_enums: Option<&[String]>,
+) -> TokenStream {
     let name_ident = Ident::new(name, Span::mixed_site());
 
+    let extern_enums = extern_enums
+        .map(|e| e.to_owned())
+        .unwrap_or_else(|| DEFAULT_EXTERN_ENUMS.iter().map(|e| e.to_string()).collect());
+
     quote! {
         #[derive(graphql_client::GraphQLQuery, Clone, Debug, serde::Deserialize, PartialEq)]
         #[graphql(
             query_path = #query_path,
             schema_path = #schema_path,
             response_derives = "Clone,Debug,PartialEq,Deserialize,Serialize",
             variables_derives = "Clone,Debug,PartialEq,Deserialize",
+            extern_enums(#(#extern_enums),*),
             skip_serializing_none
         )]
         pub struct #name_ident;
@@ -415,6 +476,24 @@ fn write_output_query_file(output_query_file_name: &str, contents: &str) {
         .unwrap_or_else(|_| panic!("Could not write to {}", output_query_file_name));
 }
 
+fn extract_extern_enums(extern_enums: &ExprArray) -> Vec<String> {
+    let extern_enum_error_msg = r#"The `extern_enums` attribute expects comma separated string literals\n\n= help: use `extern_enums = ["Enum1", "Enum2"]`"#;
+    extern_enums
+        .elems
+        .iter()
+        .map(|expr| {
+            let value = match expr {
+                Expr::Lit(lit) => lit.lit.clone(),
+                _ => panic!("{}", extern_enum_error_msg),
+            };
+            match value {
+                syn::Lit::Str(lit) => lit.value(),
+                _ => panic!("{}", extern_enum_error_msg),
+            }
+        })
+        .collect()
+}
+
 #[cfg(test)]
 mod tests {}
 
@@ -425,4 +504,5 @@ mod kw {
     syn::custom_keyword!(schema_path);
     syn::custom_keyword!(input_stream);
     syn::custom_keyword!(output_stream);
+    syn::custom_keyword!(extern_enums);
 }