codegen: enable ids to be deserialized from strings or integers

Although not strictly to spec, some upstream graphql implementations such as the start.gg
API encode their ID types as integers rather than strings. Prior to this commit,
deserialization would fail in such cases, since graphql_client simply type aliases the ID
type to a String. This commit introduces a simple deserialization helper that enables us
to handle both integers and strings while maintaining backward compatbility for downstream
users.

Fixes: #455

Signed-off-by: William Findlay <william@williamfindlay.com>

Author: willfindlay

graphql_client/src/lib.rs

@@ -30,6 +30,8 @@ pub use graphql_query_derive::*;
 ))]
 pub mod reqwest;
 
+pub mod serde_with;
+
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::fmt::{self, Display, Write};

graphql_client/src/serde_with.rs

@@ -0,0 +1,27 @@
+//! Helpers for overriding default serde implementations.
+
+use serde::{Deserialize, Deserializer};
+
+/// Deserialize an optional ID type from either a String or an Integer representation.
+///
+/// This is used by the codegen to enable String IDs to be deserialized from
+/// either Strings or Integers.
+pub fn deserialize_option_id<'de, D>(deserializer: D) -> Result<Option<String>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    enum IntOrString {
+        Int(i64),
+        Str(String),
+    }
+
+    let res = Option::<IntOrString>::deserialize(deserializer)?;
+
+    Ok(match res {
+        None => None,
+        Some(IntOrString::Int(n)) => Some(n.to_string()),
+        Some(IntOrString::Str(s)) => Some(s),
+    })
+}

graphql_client_codegen/src/codegen/selection.rs

@@ -405,6 +405,14 @@ impl<'a> ExpandedField<'a> {
             qualified_type
         };
 
+        let id_deserialize_with = if self.field_type == "ID" {
+            Some(
+                quote!(#[serde(deserialize_with = "graphql_client::serde_with::deserialize_option_id")]),
+            )
+        } else {
+            None
+        };
+
         let optional_skip_serializing_none = if *options.skip_serializing_none()
             && self
                 .field_type_qualifiers
@@ -443,6 +451,7 @@ impl<'a> ExpandedField<'a> {
             #optional_flatten
             #optional_rename
             #optional_deprecation_annotation
+            #id_deserialize_with
             pub #ident: #qualified_type
         };