[Rust] EVE Online ESI generated code does not build

Description

I am trying to build Rust bindings for EVE Online's ESI EVE Swagger Interface. Unfortunately, lists in parameters aren't always being handled correctly. Specifically, the generated API code tries to apply join(",") to Vecs of various incompatible types, including i32 and Vec<i32>.

Swagger-codegen version

I have tried with multiple versions; all seem to generate the same code. I am currently working with master from Git (f6fca7640 2018-05-03).

Swagger declaration file content or url

https://esi.tech.ccp.is/latest/swagger.json?datasource=tranquility

Command line used for generation

java -jar swagger-codegen-cli.jar generate
-i https://esi.tech.ccp.is/latest/swagger.json?datasource=tranquility
-l rust
--invoker-package esi
--api-package esi
--model-package esi
-DpackageName=esi
-o .

Steps to reproduce

Run the generator as described above. cargo build (any recent Rust version).

Related issues/PRs

None found.

Suggest a fix/enhancement

I've started to fix this: the following gross-hack patch to api.mustache gets all the cases for Vec<i32> and the like.

diff --git a/modules/swagger-codegen/src/main/resources/rust/api.mustache b/modules/swagger-codegen/src/main/resources/rust/api.mustache
index 55604ca79..ab6c69334 100644
--- a/modules/swagger-codegen/src/main/resources/rust/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/rust/api.mustache
@@ -87,7 +87,7 @@ impl<C: hyper::client::Connect>{{classname}} for {{classname}}Client<C> {
         let query_string = {
             let mut query = ::url::form_urlencoded::Serializer::new(String::new());
 {{#queryParams}}
-            query.append_pair("{{baseName}}", &{{paramName}}{{#isListContainer}}.join(","){{/isListContainer}}.to_string());
+            query.append_pair("{{baseName}}", &{{paramName}}{{#isListContainer}}.iter().map(|v| v.to_string()).collect::<Vec<String>>().join(","){{/isListContainer}}.to_string());
 {{/queryParams}}
 {{#hasAuthMethods}}
             for (key, val) in &auth_query {

Unfortunately in one case (/route/<origin>/<destination>) a parameter is a list of pairs, which gets translated to a list of lists i.e. Vec<Vec<i32>> which still fails to join(). I could conceivably kludge around this, but it seems like someone with a better understanding of the mustache templating being used here could put some more principled fix in place.

Start with modules/swagger-codegen/src/main/resources/rust/api.mustache and reproduce the issue using the documented Java generation command, then run cargo build on the generated client. Check how list and nested-list query parameters are rendered, including the route parameter case; done means the generated Rust code builds for the supplied ESI Swagger document.