Add rustfmt step to CI

Author: tomhoule

.travis.yml

@@ -4,7 +4,10 @@ rust:
   - beta
   - nightly
 cache: cargo
+before_script:
+  - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then (rustup component add rustfmt-preview) fi
 script:
+  - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then (cargo fmt --all -- --check) fi
   - cargo test --all
   - cargo build --manifest-path=./examples/github/Cargo.toml
   - cargo build --manifest-path=./graphql_client_cli/Cargo.toml

graphql_query_derive/src/unions.rs

@@ -71,14 +71,13 @@ impl GqlUnion {
                                     &new_prefix,
                                 )
                             });
-                        let field_interface =
-                            query_context.schema.interfaces.get(&frag.on).map(|_f| {
-                                query_context.maybe_expand_field(
-                                    &frag.on,
-                                    &frag.fields,
-                                    &new_prefix,
-                                )
-                            });
+                        let field_interface = query_context.schema.interfaces.get(&frag.on).map(|_f| {
+                            query_context.maybe_expand_field(
+                                &frag.on,
+                                &frag.fields,
+                                &new_prefix
+                            )
+                        });
                         // nested unions, is that even a thing?
                         let field_union_type = query_context.schema.unions.get(&frag.on).map(|_f| {
                             query_context.maybe_expand_field(&frag.on, &frag.fields, &new_prefix)