move new inference feature to unstable-stringify

_tools/check_docs.ts

@@ -42,6 +42,7 @@ const ENTRY_POINTS = [
   "../crypto/mod.ts",
   "../collections/mod.ts",
   "../csv/mod.ts",
+  "../csv/unstable_stringify.ts",
   "../data_structures/mod.ts",
   "../data_structures/unstable_bidirectional_map.ts",
   "../datetime/mod.ts",

csv/deno.json

@@ -6,6 +6,7 @@
     "./parse": "./parse.ts",
     "./parse-stream": "./parse_stream.ts",
     "./stringify": "./stringify.ts",
-    "./stringify-stream": "./stringify_stream.ts"
+    "./stringify-stream": "./stringify_stream.ts",
+    "./unstable-stringify": "./unstable_stringify.ts"
   }
 }

csv/stringify.ts

@@ -108,9 +108,9 @@ export type StringifyOptions = {
    * column of output. This is also where you can provide an explicit header
    * name for the column.
    *
-   * @default {undefined}
+   * @default {[]}
    */
-  columns?: readonly Column[] | undefined;
+  columns?: readonly Column[];
   /**
    * Whether to add a
    * {@link https://en.wikipedia.org/wiki/Byte_order_mark | byte-order mark} to the
@@ -250,14 +250,18 @@ function getValuesFromItem(
  * @example Give an array of objects without specifying columns
  * ```ts
  * import { stringify } from "@std/csv/stringify";
- * import { assertEquals } from "@std/assert/equals";
+ * import { assertThrows } from "@std/assert/throws";
  *
  * const data = [
  *   { name: "Rick", age: 70 },
  *   { name: "Morty", age: 14 },
  * ];
  *
- * assertEquals(stringify(data), `name,age\r\nRick,70\r\nMorty,14\r\n`);
+ * assertThrows(
+ *   () => stringify(data),
+ *   TypeError,
+ *   "No property accessor function was provided for object",
+ * );
  * ```
  *
  * @example Give an array of objects and specify columns with `headers: false`
@@ -425,7 +429,7 @@ export function stringify(
   data: readonly DataItem[],
   options?: StringifyOptions,
 ): string {
-  const { headers = true, separator: sep = ",", columns, bom = false } =
+  const { headers = true, separator: sep = ",", columns = [], bom = false } =
     options ?? {};
 
   if (sep.includes(QUOTE) || sep.includes(CRLF)) {
@@ -437,12 +441,7 @@ export function stringify(
     throw new TypeError(message);
   }
 
-  if (columns && !Array.isArray(columns)) {
-    throw new TypeError("Invalid type: columns can only be an array");
-  }
-
-  const definedColumns = columns ?? inferColumns(data);
-  const normalizedColumns = definedColumns.map(normalizeColumn);
+  const normalizedColumns = columns.map(normalizeColumn);
   let output = "";
 
   if (bom) {
@@ -466,19 +465,3 @@ export function stringify(
 
   return output;
 }
-
-/**
- * Infers the columns from the first object element of the given array.
- */
-function inferColumns(data: readonly DataItem[]): string[] {
-  const firstElement = data.at(0);
-  if (
-    firstElement &&
-    typeof firstElement === "object" &&
-    !Array.isArray(firstElement)
-  ) {
-    return Object.keys(firstElement);
-  }
-
-  return [];
-}

csv/stringify_stream.ts

@@ -99,7 +99,7 @@ export class CsvStringifyStream<TOptions extends CsvStringifyStreamOptions>
    * @param options Options for the stream.
    */
   constructor(options?: TOptions) {
-    const { separator, columns } = options ?? {};
+    const { separator, columns = [] } = options ?? {};
 
     super(
       {

csv/stringify_stream_test.ts

@@ -64,7 +64,7 @@ Deno.test({
       await assertRejects(
         async () => await Array.fromAsync(readable),
         TypeError,
-        "Invalid type: columns can only be an array",
+        "No property accessor function was provided for object",
       );
     });
 
@@ -90,12 +90,10 @@ Deno.test({
         { id: 3, name: "baz" },
         // @ts-expect-error `columns` option is required
       ]).pipeThrough(new CsvStringifyStream());
-      const output = await Array.fromAsync(readable);
-      assertEquals(output, [
-        "1,foo\r\n",
-        "2,bar\r\n",
-        "3,baz\r\n",
-      ]);
+      await assertRejects(
+        async () => await Array.fromAsync(readable),
+        TypeError,
+      );
     });
   },
 });

csv/stringify_test.ts

@@ -72,6 +72,20 @@ Deno.test({
         },
       },
     );
+
+    await t.step(
+      {
+        name: "Invalid data, no columns",
+        fn() {
+          const data = [{ a: 1 }, { a: 2 }];
+          assertThrows(
+            () => stringify(data),
+            TypeError,
+            "No property accessor function was provided for object",
+          );
+        },
+      },
+    );
     await t.step(
       {
         name: "No data, no columns",
@@ -564,27 +578,5 @@ Deno.test({
         });
       },
     });
-    await t.step(
-      {
-        name:
-          "Object array with no columns, should infer columns from the first array element",
-        fn() {
-          const data = [{ a: 1 }, { a: 2 }, { b: 3 }];
-          const output = `a${CRLF}1${CRLF}2${CRLF}${CRLF}`;
-          assertEquals(stringify(data), output);
-        },
-      },
-    );
-    await t.step(
-      {
-        name: "Object array with columns, shouldn't infer columns",
-        fn() {
-          const data = [{ a: 1 }, { a: 2 }, { b: 3 }];
-          const columns = ["a"];
-          const output = `a${CRLF}1${CRLF}2${CRLF}${CRLF}`;
-          assertEquals(stringify(data, { columns }), output);
-        },
-      },
-    );
   },
 });