Allow @deprecated directive on field args

[jonbretman]

Fixes #204

[jonbretman]

@tonyghita any thoughts?

[tonyghita]

Is this part of the specification? I'd like to avoid straying too far from the spec.

[jonbretman]

I believe so. It’s mentioned in the spec under InputValueDefinition - http://facebook.github.io/graphql/draft/#InputValueDefinition

[tonyghita]

The specification for InputValueDefinition mentions directives, but the introspection specification leaves out deprecations on __InputValue: http://facebook.github.io/graphql/draft/#sec-Schema-Introspection.

I think without special isDeprecated fields on introspection, this change would not be very useful.
Here's an issue on the GraphQL specification specifically for this functionality: graphql/graphql-spec#197

I'm going to close this change until the issue in the specification is resolved.

[jonbretman]

Fair enough, thanks for looking into it.

[smitt04]

This is working its way into the spec graphql/graphql-spec#525

[tonyghita]

We're open to adding it once it is accepted into the specification 👍

[sqs]

It is now added into the specification: graphql/graphql-spec#805 (comment)

[sqs]

And here is the diff that seems to work. Happy to submit another PR.

diff --git a/example/social/introspect.json b/example/social/introspect.json
index 795803f..e474d79 100644
--- a/example/social/introspect.json
+++ b/example/social/introspect.json
@@ -17,7 +17,8 @@
         "description": "Marks an element of a GraphQL schema as no longer supported.",
         "locations": [
           "FIELD_DEFINITION",
-          "ENUM_VALUE"
+          "ENUM_VALUE",
+          "ARGUMENT_DEFINITION"
         ],
         "name": "deprecated"
       },
diff --git a/example/starwars/introspect.json b/example/starwars/introspect.json
index a25eace..009799f 100644
--- a/example/starwars/introspect.json
+++ b/example/starwars/introspect.json
@@ -17,7 +17,8 @@
         "description": "Marks an element of a GraphQL schema as no longer supported.",
         "locations": [
           "FIELD_DEFINITION",
-          "ENUM_VALUE"
+          "ENUM_VALUE",
+          "ARGUMENT_DEFINITION"
         ],
         "name": "deprecated"
       },
diff --git a/graphql_test.go b/graphql_test.go
index 76240d5..cb240d6 100644
--- a/graphql_test.go
+++ b/graphql_test.go
@@ -1180,8 +1180,8 @@ func TestFragments(t *testing.T) {
                        `,
                },
                {
-                       Schema:         starwarsSchema,
-                       Query:          `
+                       Schema: starwarsSchema,
+                       Query: `
                                query {
                                        human(id: "1000") {
                                                id
@@ -1733,6 +1733,24 @@ func TestEnums(t *testing.T) {
        })
 }
 
+type testDeprecatedArgsResolver struct{}
+
+func (r *testDeprecatedArgsResolver) A(ctx context.Context, args struct{ B *string }) int32 {
+       return 0
+}
+
+func TestDeprecatedArgs(t *testing.T) {
+       graphql.MustParseSchema(`
+               schema {
+                       query: Query
+               }
+
+               type Query {
+                       a(b: String @deprecated): Int!
+               }
+       `, &testDeprecatedArgsResolver{})
+}
+
 func TestInlineFragments(t *testing.T) {
        gqltesting.RunTests(t, []*gqltesting.Test{
                {
@@ -2506,7 +2524,8 @@ func TestIntrospection(t *testing.T) {
                                                                        "description": "Marks an element of a GraphQL schema as no longer supported.",
                                                                        "locations": [
                                                                                "FIELD_DEFINITION",
-                                                                               "ENUM_VALUE"
+                                                                               "ENUM_VALUE",
+                                                                               "ARGUMENT_DEFINITION"
                                                                        ],
                                                                        "args": [
                                                                                {
diff --git a/internal/common/values.go b/internal/common/values.go
index 2d6e0b5..33f63d2 100644
--- a/internal/common/values.go
+++ b/internal/common/values.go
@@ -27,9 +27,11 @@ func ParseArgumentList(l *Lexer) types.ArgumentList {
                name := l.ConsumeIdentWithLoc()
                l.ConsumeToken(':')
                value := ParseLiteral(l, false)
+               directives := ParseDirectives(l)
                args = append(args, &types.Argument{
-                       Name:  name,
-                       Value: value,
+                       Name:       name,
+                       Value:      value,
+                       Directives: directives,
                })
        }
        l.ConsumeToken(')')
diff --git a/internal/schema/meta.go b/internal/schema/meta.go
index 154c07c..7941a63 100644
--- a/internal/schema/meta.go
+++ b/internal/schema/meta.go
@@ -57,7 +57,7 @@ var metaSrc = `
                # for how to access supported similar data. Formatted in
                # [Markdown](https://daringfireball.net/projects/markdown/).
                reason: String = "No longer supported"
-       ) on FIELD_DEFINITION | ENUM_VALUE
+       ) on FIELD_DEFINITION | ENUM_VALUE | ARGUMENT_DEFINITION
 
        # Provides a scalar specification URL for specifying the behavior of custom scalar types.
        directive @specifiedBy(
diff --git a/types/argument.go b/types/argument.go
index b2681a2..72329da 100644
--- a/types/argument.go
+++ b/types/argument.go
@@ -4,8 +4,9 @@ package types
 //
 // https://spec.graphql.org/draft/#sec-Language.Arguments
 type Argument struct {
-       Name  Ident
-       Value Value
+       Name       Ident
+       Value      Value
+       Directives DirectiveList
 }
 
 // ArgumentList is a collection of GraphQL Arguments.

[pavelnikolov]

@sqs thank you for commenting. Could you, please, open a new PR? I would be happy to review and merge it.

[pavelnikolov]

@sqs I took the changes and raised a PR myself.