Parse years and months as string fields

Closes #10

Author: marcusolsson

src/DataSource.ts

@@ -133,9 +133,9 @@ export class DataSource extends DataSourceApi<JsonApiQuery, JsonApiDataSourceOpt
  * @param values - The field values.
  * @returns the detected field type and potentially converted values.
  */
-const detectFieldType = (values: any[]): [FieldType, any[]] => {
+export const detectFieldType = (values: any[]): [FieldType, any[]] => {
   // If all values are valid ISO 8601, the assume that it's a time field.
-  const isValidISO = values.every(value => isValid(parseISO(value)));
+  const isValidISO = values.every(value => value.length >= 10 && isValid(parseISO(value)));
   if (isValidISO) {
     return [FieldType.time, values.map(_ => parseISO(_).valueOf())];
   }

src/detectFieldType.test.ts

@@ -0,0 +1,14 @@
+import { detectFieldType } from './DataSource';
+
+test('years and months gets parsed as string to reduce false positives', () => {
+  expect(detectFieldType(['2005', '2006'])).toEqual(['string', ['2005', '2006']]);
+  expect(detectFieldType(['2005-01', '2006-01'])).toEqual(['string', ['2005-01', '2006-01']]);
+});
+
+test('iso8601 gets parsed as time', () => {
+  expect(detectFieldType(['2005-01-02', '2006-01-02'])).toEqual(['time', [1104620400000, 1136156400000]]);
+  expect(detectFieldType(['2006-01-02T15:06:13Z', '2006-01-02T15:07:13Z'])).toEqual([
+    'time',
+    [1136214373000, 1136214433000],
+  ]);
+});