test(csv-stringify): columns type test as const

Author: wdavidw

packages/csv-stringify/dist/cjs/index.d.cts

@@ -61,7 +61,7 @@ export interface Options extends stream.TransformOptions {
      * can refer to nested properties of the input JSON
      * see the "header" option on how to print columns names on the first line
      */
-    columns?: string[] | PlainObject<string> | ColumnOption[]
+    columns?: readonly string[] | PlainObject<string> | readonly ColumnOption[]
     /**
      * Set the field delimiter, one character only, defaults to a comma.
      */

packages/csv-stringify/dist/esm/index.d.ts

@@ -61,7 +61,7 @@ export interface Options extends stream.TransformOptions {
      * can refer to nested properties of the input JSON
      * see the "header" option on how to print columns names on the first line
      */
-    columns?: string[] | PlainObject<string> | ColumnOption[]
+    columns?: readonly string[] | PlainObject<string> | readonly ColumnOption[]
     /**
      * Set the field delimiter, one character only, defaults to a comma.
      */

packages/csv-stringify/test/api.types.sync.ts

@@ -20,7 +20,7 @@ describe('API Types', () => {
       const rd: RecordDelimiter | undefined = options.record_delimiter
       const cast = options.cast
       const castBoolean : Cast<boolean> | undefined = cast?.boolean
-      const columns: string[] | PlainObject<string> | ColumnOption[] | undefined = options.columns
+      const columns: readonly string[] | PlainObject<string> | readonly ColumnOption[] | undefined = options.columns
       return [
         rd, castBoolean, columns
       ]

packages/csv-stringify/test/api.types.ts

@@ -1,6 +1,7 @@
 
 import 'should'
 import { stringify, CastingContext, Options, Stringifier } from '../lib/index.js'
+import { stringify as stringifySync } from '../lib/index.js'
 
 describe('API Types', () => {
 
@@ -74,6 +75,12 @@ describe('API Types', () => {
         field3: 'column3'
       }
     })
+      
+    it("columns as const", () => {
+      const options: Options = {};
+      options.columns = ["b", "a"];
+      options.columns = ["b", "a"] as const;
+    });
 
     it('delimiter', () => {
       const options: Options = {}