[schema] Remove empty input fields

packages/gatsby/src/schema/types/__tests__/filter-input.js

@@ -0,0 +1,56 @@
+const { build } = require(`../..`)
+const { store } = require(`../../../redux`)
+require(`../../../db/__tests__/fixtures/ensure-loki`)()
+
+const nodes = [
+  {
+    id: `parent`,
+    nested: {
+      union___NODE: [`union1`, `union2`],
+    },
+    internal: {
+      type: `Parent`,
+      contentDigest: `a`,
+    },
+  },
+  {
+    id: `union1`,
+    foo: `bar`,
+    internal: {
+      type: `Union1`,
+      contentDigest: `bar`,
+    },
+  },
+  {
+    id: `union2`,
+    foo: `baz`,
+    internal: {
+      type: `Union2`,
+      contentDigest: `baz`,
+    },
+  },
+]
+
+describe(`Filter input`, () => {
+  beforeEach(async () => {
+    store.dispatch({ type: `DELETE_CACHE` })
+    nodes.forEach(node =>
+      store.dispatch({ type: `CREATE_NODE`, payload: { ...node } })
+    )
+  })
+
+  it(`removes empty input filter fields`, async () => {
+    // This can happen when a type has only one GraphQLUnion type field,
+    // which will be skipped by `toInputObjectType`
+    const schema = await buildSchema()
+    const parentFilterInput = schema.getType(`ParentFilterInput`)
+    const fields = parentFilterInput.getFields()
+    expect(fields.id).toBeDefined()
+    expect(fields.nested).toBeUndefined()
+  })
+})
+
+const buildSchema = async () => {
+  await build({})
+  return store.getState().schema
+}

packages/gatsby/src/schema/types/filter.js

@@ -72,6 +72,34 @@ const convert = ({
   return convertedITC
 }
 
+const removeEmptyFields = (
+  { schemaComposer, inputTypeComposer },
+  cache = new Set()
+) => {
+  const convert = itc => {
+    if (cache.has(itc)) {
+      return itc
+    }
+    cache.add(itc)
+    const fields = itc.getFields()
+    const nonEmptyFields = {}
+    Object.keys(fields).forEach(fieldName => {
+      const fieldITC = fields[fieldName]
+      if (fieldITC instanceof schemaComposer.InputTypeComposer) {
+        const convertedITC = convert(fieldITC)
+        if (convertedITC.getFieldNames().length) {
+          nonEmptyFields[fieldName] = convertedITC
+        }
+      } else {
+        nonEmptyFields[fieldName] = fieldITC
+      }
+    })
+    itc.setFields(nonEmptyFields)
+    return itc
+  }
+  return convert(inputTypeComposer)
+}
+
 const getFilterInput = ({ schemaComposer, typeComposer }) => {
   const typeName = typeComposer.getTypeName()
   const filterInputComposer = schemaComposer.getOrCreateITC(
@@ -88,11 +116,13 @@ const getFilterInput = ({ schemaComposer, typeComposer }) => {
     inputTypeComposer.extendField(`id`, { type: `String` })
   }
 
-  return convert({
+  const filterInputTC = convert({
     schemaComposer,
     inputTypeComposer,
     filterInputComposer,
   })
+
+  return removeEmptyFields({ schemaComposer, inputTypeComposer: filterInputTC })
 }
 
 module.exports = { getFilterInput }