How to use the CLI client to generate a schema?

[djc]

I've built a Juniper-based GraphQL server this week and now I'd like to execute tests against it. This project seems like the best way to do so from Rust, and so I'm trying to generate a schema for my server. The built-in GraphiQL instance can read the introspection data just fine, but when I run graphql-client introspect-schema http://localhost:3000/graphql I just get {"data":{"schema":null},"errors":null}.

(Just to be sure, I get the same result if I run introspect-schema against the GitHub GraphQL endpoint.)

What, if anything, am I getting wrong?

[tomhoule]

I haven't paid attention to the CLI since its initial release nearly two months ago so it may have broken. I will definitely investigate this asap but as a temporary solution you can use https://github.com/apollographql/apollo-cli for introspecting and downloading the schema.json

[djc]

I have been investigating, but can't quite figure it out. As far as I can tell the problem is in the deserialization of the introspection query result -- can you recommend any techniques for debugging the deserialization code that runs during GraphQLResponse deserialization?

(Apollo is not a great option for me since I don't have Node.js/npm tooling installed, and I'd like to keep it that way.)

[tomhoule]

The weird thing is that the CLI should panic in the event of a serde error, so the schema field in ResponseData was null (or absent). I don't remember exactly right now, but it might be __schema instead, I'll have time to investigate later today. If it happens with the github API as well I can probably reproduce the issue.

[djc]

Here's the response from my server: https://gist.githubusercontent.com/djc/c7de96fdb8e4e6839ec3f32045408a9f/raw/e86794a82cfd13cefd831bdb9686cbd0a1ee6830/introspection-result.json

[tomhoule]

Thanks! now think I know what the problem is: the root field of ResponseData should actually be __schema but we transform between snake and camel case, and the leading underscores most likely get swallowed. The CLI should be tested :/ I can't fix this right away, but I will do this evening - if you want to do it it's also welcome of course.

edit: not so sure anymore. we use #[serde(rename = "theCamelCaseName")] on structs, it could be missing on ResponseData.

[djc]

So yeah, this change seems to at least get me some output:

diff --git a/graphql_query_derive/src/codegen.rs b/graphql_query_derive/src/codegen.rs
index f9501ca..34ece7a 100644
--- a/graphql_query_derive/src/codegen.rs
+++ b/graphql_query_derive/src/codegen.rs
@@ -120,7 +121,7 @@ pub(crate) fn response_for_query(
         #variables_struct
 
         #[derive(Debug, Serialize, Deserialize)]
-        #[serde(rename_all = "camelCase")]
+        //#[serde(rename_all = "camelCase")]
         pub struct ResponseData {
             #(#response_data_fields,)*
         }
diff --git a/graphql_query_derive/src/shared.rs b/graphql_query_derive/src/shared.rs
index 73332ff..e425920 100644
--- a/graphql_query_derive/src/shared.rs
+++ b/graphql_query_derive/src/shared.rs
@@ -20,7 +20,22 @@ pub(crate) fn render_object_field(
         };
     }
 
-    let name_ident = Ident::new(&field_name.to_snake_case(), Span::call_site());
+    let mut snake_case = field_name.to_snake_case();
+    let mut leading_underscores = 0;
+    for (i, c) in field_name.as_bytes().iter().enumerate() {
+        if *c != b'_' {
+            leading_underscores = i;
+            break;
+        }
+    }
+
+    if leading_underscores > 0 {
+        let mut new = field_name[..leading_underscores].to_string();
+        new.push_str(&snake_case);
+        snake_case = new;
+    }
+    let name_ident = Ident::new(&snake_case, Span::call_site());
 
     quote!(#description pub #name_ident: #field_type)
 }

But that means neither heck nor serde camel case conversions do what we need for GraphQL here...

[djc]

The schema JSON generated with that patch still caused problems with some missing fields.

This seems to be much more effective, though:

diff --git a/graphql_client_cli/src/main.rs b/graphql_client_cli/src/main.rs
index 5e5a387..253600d 100644
--- a/graphql_client_cli/src/main.rs
+++ b/graphql_client_cli/src/main.rs
@@ -85,10 +85,7 @@ fn introspect_schema(location: String, output: Option<PathBuf>) -> Result<(), fa
         println!("Something else happened. Status: {:?}", res.status());
     }
 
-    let json: graphql_client::GraphQLResponse<introspection_query::ResponseData> = res.json()?;
-    let json = serde_json::to_string(&json)?;
-
-    write!(out, "{}", json)?;
-
-    Ok(())
+    //let json: graphql_client::GraphQLResponse<introspection_query::ResponseData> = res.json()?;
+    let json: serde_json::Value = res.json()?;
+    Ok(serde_json::to_writer_pretty(out, &json)?)
 }

[tomhoule]

Oh indeed, that's a nice workaround.

[tomhoule]

I'm writing a test for the underscore issue, we can merge a quick PR with your fix. I was planning to release today or just wait for the next nightly release (current one has a known bug that makes graphql-client's macros fail).

[tomhoule]

So the culprit for swallowing leading underscores is #[serde(rename_all = "camelCase")] apparently. For correctness it should rename to whatever the name of the field is in the schema. It shouldn't be too hard to correct, I'm on the bug in any case, thanks for discovering it, and sorry that you did.

[djc]

At this point I'm a bit wary of the round-trip through ResponseData, what is the point? Just taking the JSON result from the introspection query seems pretty good.

Note that I've tried to actually derive a simple mutation query, and I ran into trouble again. The expand() method mentioned in the README doesn't seem to get generated.

[tomhoule]

For now it's definitely a better option to just dump the whole response - if I remember correctly the idea was that we could have a nice error message if the response wasn't a valid schema, but it's supposing things are working. I'll look into the expand issue too.

[tomhoule]

Oh my, the README example is out of date... You can check out the api docs, they are tested: https://docs.rs/graphql_client/latest/graphql_client/trait.GraphQLQuery.html

This will be fixed in the coming release.