planning

node_modules/apollo-utilities/src/fragments.ts

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+import { DocumentNode, FragmentDefinitionNode } from 'graphql';
+import { invariant, InvariantError } from 'ts-invariant';
+
+/**
+ * Returns a query document which adds a single query operation that only
+ * spreads the target fragment inside of it.
+ *
+ * So for example a document of:
+ *
+ * ```graphql
+ * fragment foo on Foo { a b c }
+ * ```
+ *
+ * Turns into:
+ *
+ * ```graphql
+ * { ...foo }
+ *
+ * fragment foo on Foo { a b c }
+ * ```
+ *
+ * The target fragment will either be the only fragment in the document, or a
+ * fragment specified by the provided `fragmentName`. If there is more than one
+ * fragment, but a `fragmentName` was not defined then an error will be thrown.
+ */
+export function getFragmentQueryDocument(
+  document: DocumentNode,
+  fragmentName?: string,
+): DocumentNode {
+  let actualFragmentName = fragmentName;
+
+  // Build an array of all our fragment definitions that will be used for
+  // validations. We also do some validations on the other definitions in the
+  // document while building this list.
+  const fragments: Array<FragmentDefinitionNode> = [];
+  document.definitions.forEach(definition => {
+    // Throw an error if we encounter an operation definition because we will
+    // define our own operation definition later on.
+    if (definition.kind === 'OperationDefinition') {
+      throw new InvariantError(
+        `Found a ${definition.operation} operation${
+          definition.name ? ` named '${definition.name.value}'` : ''
+        }. ` +
+          'No operations are allowed when using a fragment as a query. Only fragments are allowed.',
+      );
+    }
+    // Add our definition to the fragments array if it is a fragment
+    // definition.
+    if (definition.kind === 'FragmentDefinition') {
+      fragments.push(definition);
+    }
+  });
+
+  // If the user did not give us a fragment name then let us try to get a
+  // name from a single fragment in the definition.
+  if (typeof actualFragmentName === 'undefined') {
+    invariant(
+      fragments.length === 1,
+      `Found ${
+        fragments.length
+      } fragments. \`fragmentName\` must be provided when there is not exactly 1 fragment.`,
+    );
+    actualFragmentName = fragments[0].name.value;
+  }
+
+  // Generate a query document with an operation that simply spreads the
+  // fragment inside of it.
+  const query: DocumentNode = {
+    ...document,
+    definitions: [
+      {
+        kind: 'OperationDefinition',
+        operation: 'query',
+        selectionSet: {
+          kind: 'SelectionSet',
+          selections: [
+            {
+              kind: 'FragmentSpread',
+              name: {
+                kind: 'Name',
+                value: actualFragmentName,
+              },
+            },
+          ],
+        },
+      },
+      ...document.definitions,
+    ],
+  };
+
+  return query;
+}