Add GraphQL fragment support (#2005)

src/printer-graphql.js

@@ -48,6 +48,16 @@ function genericPrint(path, options, print) {
         path.call(print, "selectionSet")
       ]);
     }
+    case "FragmentDefinition": {
+      return concat([
+        "fragment ",
+        path.call(print, "name"),
+        " on ",
+        path.call(print, "typeCondition"),
+        " ",
+        path.call(print, "selectionSet")
+      ]);
+    }
     case "SelectionSet": {
       return concat([
         "{",
@@ -141,6 +151,21 @@ function genericPrint(path, options, print) {
       ]);
     }
 
+    case "FragmentSpread": {
+      return concat(["...", path.call(print, "name")]);
+    }
+
+    case "InlineFragment": {
+      return concat([
+        "...",
+        n.typeCondition
+          ? concat([" on ", path.call(print, "typeCondition")])
+          : "",
+        " ",
+        path.call(print, "selectionSet")
+      ]);
+    }
+
     default:
       throw new Error("unknown graphql type: " + JSON.stringify(n.kind));
   }

tests/graphql_fragments/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,35 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`fragments.graphql 1`] = `
+{
+  field
+  ...   XYZ
+  ... on TheType {
+    ...AFragment
+    ...          {
+      noTypeCondition
+    }
+  }
+}
+
+fragment XYZ on ABC {
+  field
+  ...AFragment
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+{
+  field
+  ...XYZ
+  ... on TheType {
+    ...AFragment
+    ... {
+      noTypeCondition
+    }
+  }
+}
+
+fragment XYZ on ABC {
+  field
+  ...AFragment
+}
+`;

tests/graphql_fragments/fragments.graphql

@@ -0,0 +1,15 @@
+{
+  field
+  ...   XYZ
+  ... on TheType {
+    ...AFragment
+    ...          {
+      noTypeCondition
+    }
+  }
+}
+
+fragment XYZ on ABC {
+  field
+  ...AFragment
+}

tests/graphql_fragments/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "graphql" });