Automatically determine scalar types.

README.md

@@ -24,7 +24,7 @@ Usage
 Construct a GraphQL client, specifying the GraphQL server URL. Then, you can use it to make GraphQL queries and mutations.
 
 ```Go
-client := graphql.NewClient("https://example.com/graphql", nil, nil)
+client := graphql.NewClient("https://example.com/graphql", nil)
 // Use client...
 ```
 
@@ -41,7 +41,7 @@ func main() {
 	)
 	httpClient := oauth2.NewClient(context.Background(), src)
 
-	client := graphql.NewClient("https://example.com/graphql", httpClient, nil)
+	client := graphql.NewClient("https://example.com/graphql", httpClient)
 	// Use client...
 ```
 

example/graphqldev/main.go

@@ -38,7 +38,7 @@ func run() error {
 	mux := http.NewServeMux()
 	mux.Handle("/query", &relay.Handler{Schema: schema})
 
-	client := graphql.NewClient("/query", &http.Client{Transport: localRoundTripper{handler: mux}}, nil)
+	client := graphql.NewClient("/query", &http.Client{Transport: localRoundTripper{handler: mux}})
 
 	/*
 		query {

graphql.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
-	"reflect"
 
 	"github.com/shurcooL/go/ctxhttp"
 	"github.com/shurcooL/graphql/internal/jsonutil"
@@ -16,25 +15,17 @@ import (
 type Client struct {
 	url        string // GraphQL server URL.
 	httpClient *http.Client
-
-	qctx *queryContext
 }
 
 // NewClient creates a GraphQL client targeting the specified GraphQL server URL.
 // If httpClient is nil, then http.DefaultClient is used.
-// scalars optionally specifies types that are scalars (this matters
-// when constructing queries from types, scalars are never expanded).
-func NewClient(url string, httpClient *http.Client, scalars []reflect.Type) *Client {
+func NewClient(url string, httpClient *http.Client) *Client {
 	if httpClient == nil {
 		httpClient = http.DefaultClient
 	}
 	return &Client{
 		url:        url,
 		httpClient: httpClient,
-
-		qctx: &queryContext{
-			Scalars: scalars,
-		},
 	}
 }
 
@@ -57,9 +48,9 @@ func (c *Client) do(ctx context.Context, op operationType, v interface{}, variab
 	var query string
 	switch op {
 	case queryOperation:
-		query = constructQuery(c.qctx, v, variables)
+		query = constructQuery(v, variables)
 	case mutationOperation:
-		query = constructMutation(c.qctx, v, variables)
+		query = constructMutation(v, variables)
 	}
 	in := struct {
 		Query     string                 `json:"query"`

query.go

@@ -2,23 +2,24 @@ package graphql
 
 import (
 	"bytes"
+	"encoding/json"
 	"io"
 	"reflect"
 	"sort"
 
 	"github.com/shurcooL/graphql/ident"
 )
 
-func constructQuery(qctx *queryContext, v interface{}, variables map[string]interface{}) string {
-	query := qctx.Query(v)
+func constructQuery(v interface{}, variables map[string]interface{}) string {
+	query := query(v)
 	if variables != nil {
 		return "query(" + queryArguments(variables) + ")" + query
 	}
 	return query
 }
 
-func constructMutation(qctx *queryContext, v interface{}, variables map[string]interface{}) string {
-	query := qctx.Query(v)
+func constructMutation(v interface{}, variables map[string]interface{}) string {
+	query := query(v)
 	if variables != nil {
 		return "mutation(" + queryArguments(variables) + ")" + query
 	}
@@ -58,33 +59,26 @@ func queryArguments(variables map[string]interface{}) string {
 	return s
 }
 
-type queryContext struct {
-	// Scalars are Go types that map to GraphQL scalars, and therefore we don't want to expand them.
-	Scalars []reflect.Type
-}
-
-// Query uses writeQuery to recursively construct
+// query uses writeQuery to recursively construct
 // a minified query string from the provided struct v.
 //
 // E.g., struct{Foo Int, BarBaz *Boolean} -> "{foo,barBaz}".
-func (c *queryContext) Query(v interface{}) string {
+func query(v interface{}) string {
 	var buf bytes.Buffer
-	c.writeQuery(&buf, reflect.TypeOf(v), false)
+	writeQuery(&buf, reflect.TypeOf(v), false)
 	return buf.String()
 }
 
 // writeQuery writes a minified query for t to w. If inline is true,
 // the struct fields of t are inlined into parent struct.
-func (c *queryContext) writeQuery(w io.Writer, t reflect.Type, inline bool) {
+func writeQuery(w io.Writer, t reflect.Type, inline bool) {
 	switch t.Kind() {
 	case reflect.Ptr, reflect.Slice:
-		c.writeQuery(w, t.Elem(), false)
+		writeQuery(w, t.Elem(), false)
 	case reflect.Struct:
-		// Special handling of scalar struct types. Don't expand them.
-		for _, scalar := range c.Scalars {
-			if t == scalar {
-				return
-			}
+		// If the type implements json.Unmarshaler, it's a scalar. Don't expand it.
+		if reflect.PtrTo(t).Implements(jsonUnmarshaler) {
+			return
 		}
 		if !inline {
 			io.WriteString(w, "{")
@@ -103,10 +97,12 @@ func (c *queryContext) writeQuery(w io.Writer, t reflect.Type, inline bool) {
 					io.WriteString(w, ident.ParseMixedCaps(f.Name).ToLowerCamelCase())
 				}
 			}
-			c.writeQuery(w, f.Type, inlineField)
+			writeQuery(w, f.Type, inlineField)
 		}
 		if !inline {
 			io.WriteString(w, "}")
 		}
 	}
 }
+
+var jsonUnmarshaler = reflect.TypeOf((*json.Unmarshaler)(nil)).Elem()

query_test.go

@@ -2,7 +2,6 @@ package graphql
 
 import (
 	"net/url"
-	"reflect"
 	"testing"
 	"time"
 )
@@ -217,15 +216,20 @@ func TestConstructQuery(t *testing.T) {
 			}(),
 			want: `{actor{login,avatarUrl,url},createdAt,... on IssueComment{body},currentTitle,previousTitle,label{name,color}}`,
 		},
+		{
+			inV: struct {
+				Viewer struct {
+					Login      string
+					CreatedAt  time.Time
+					ID         interface{}
+					DatabaseID int
+				}
+			}{},
+			want: `{viewer{login,createdAt,id,databaseId}}`,
+		},
 	}
 	for _, tc := range tests {
-		qctx := &queryContext{
-			Scalars: []reflect.Type{
-				reflect.TypeOf(DateTime{}),
-				reflect.TypeOf(URI{}),
-			},
-		}
-		got := constructQuery(qctx, tc.inV, tc.inVariables)
+		got := constructQuery(tc.inV, tc.inVariables)
 		if got != tc.want {
 			t.Errorf("\ngot:  %q\nwant: %q\n", got, tc.want)
 		}
@@ -260,7 +264,7 @@ func TestConstructMutation(t *testing.T) {
 		},
 	}
 	for _, tc := range tests {
-		got := constructMutation(&queryContext{}, tc.inV, tc.inVariables)
+		got := constructMutation(tc.inV, tc.inVariables)
 		if got != tc.want {
 			t.Errorf("\ngot:  %q\nwant: %q\n", got, tc.want)
 		}
@@ -311,6 +315,8 @@ type (
 	URI struct{ *url.URL }
 )
 
+func (u *URI) UnmarshalJSON(data []byte) error { panic("mock implementation") }
+
 // IssueState represents the possible states of an issue.
 type IssueState string