Merge pull request #19 from specialblend/feat/path-head

feat: path head option

README.md

@@ -276,6 +276,61 @@ query GetAddresses2 {
 
 ❓ [see example unit tests.](example/GetAddresses.example.test.ts)
 
+#### using JSONPath on array fields
+
+By default, mapql will return head (first element) of result from JSONPath query. This can be disabled with argument `head: false`, useful when expecting list of values. Default value is `head: true`.
+
+example:
+
+```javascript
+const data = {
+    exampleObj: {
+        exampleStr: "hello world",
+    },
+    destinations: [
+        {
+            array_string: "foo",
+        },
+        {
+            array_string: "bar",
+        },
+        {
+            array_string: "baz",
+        },
+    ],
+}
+```
+
+```graphql
+    query PathHead {
+      exampleStr
+      exampleStrHead(head: true)
+      exampleStrNoHead(head: false)
+      destinationsHead(from: "destinations[*].array_string", head: true)
+      destinationsNoHead(from: "destinations[*].array_string", head: false)
+      destinations(from: "destinations[*].array_string")
+    }
+```
+
+```json
+{
+  "destinations": "foo",
+  "destinationsHead": "foo",
+  "destinationsNoHead": [
+    "foo",
+    "bar",
+    "baz"
+  ],
+  "exampleStr": "hello world",
+  "exampleStrHead": "hello world",
+  "exampleStrNoHead": [
+    "hello world"
+  ]
+}
+```
+
+❓ [see example unit tests.](example/PathHead.example.test.ts)
+
 ### filtering fields
 
 ⭕ query:

example/PathHead.example.test.ts

@@ -0,0 +1,43 @@
+import gql from "graphql-tag";
+import map from "../src";
+
+test("PathHead", () => {
+  const data = {
+    exampleObj: {
+      exampleStr: "hello world",
+    },
+    destinations: [
+      {
+        array_string: "foo",
+      },
+      {
+        array_string: "bar",
+      },
+      {
+        array_string: "baz",
+      },
+    ],
+  };
+  const query = gql`
+    query PathHead {
+      exampleStr(from: "exampleObj.exampleStr")
+      exampleStrHead(from: "exampleObj.exampleStr", head: true)
+      exampleStrNoHead(from: "exampleObj.exampleStr", head: false)
+      destinationsHead(from: "destinations[*].array_string", head: true)
+      destinationsNoHead(from: "destinations[*].array_string", head: false)
+      destinations(from: "destinations[*].array_string")
+    }
+  `;
+  const result = map(query, data);
+  expect(result).toEqual(
+    //
+    {
+      destinations: "foo",
+      destinationsHead: "foo",
+      destinationsNoHead: ["foo", "bar", "baz"],
+      exampleStr: "hello world",
+      exampleStrHead: "hello world",
+      exampleStrNoHead: ["hello world"],
+    }
+  );
+});

src/contract.ts

@@ -25,6 +25,7 @@ export type ExecSource = JsonRecord;
 export interface ExecArgs {
   from?: PathSelector;
   filter?: Filter;
+  head?: boolean;
 }
 
 export type Exec = {

src/exec.ts

@@ -69,11 +69,11 @@ function execPath(ex: Exec) {
     const {
       fieldName,
       root,
-      args: { from },
+      args: { from, head = true },
     } = ex;
     if (shouldExPath(ex)) {
       const pathName = isset(from) ? from : fieldName;
-      return path(pathName, data, root);
+      return path(pathName, data, root, head);
     }
     return root;
   };

src/path.ts

@@ -7,25 +7,31 @@ import type {
 } from "./contract";
 
 import jp from "jsonpath";
-import { isset } from "./util";
 
-function jsonpath(selector: string, data: JsonParent): Maybe<JsonChild> {
-  const [child] = jp.query(data, selector);
-  if (isset(child)) {
-    return child;
+function jsonpath(
+  selector: string,
+  data: JsonParent,
+  head = true
+): Maybe<JsonChild> {
+  const result = jp.query(data, selector);
+  const [first] = result;
+  if (head) {
+    return first;
   }
+  return result;
 }
 
 export function path(
   selector: PathSelector,
   source: JsonRecord,
-  parent: JsonParent = source
+  parent: JsonParent = source,
+  head = true
 ): Maybe<JsonChild> {
   if (selector === "@") {
     return jsonpath("$", parent);
   }
   if (selector[0] === "$") {
-    return jsonpath(selector, source);
+    return jsonpath(selector, source, head);
   }
-  return jsonpath(selector, parent);
+  return jsonpath(selector, parent, head);
 }