readCSV: ignore trailing empty lines

reader.ts

@@ -709,10 +709,12 @@ export function readCSVRows(
 
 class RowIterator implements AsyncIterableIterator<string> {
   private onRequested: () => Promise<IteratorResult<string | symbol>>;
+  private buffer: Array<IteratorResult<string | symbol>>;
   private done: boolean;
 
   constructor(onRequested: () => Promise<IteratorResult<string | symbol>>) {
     this.onRequested = onRequested;
+    this.buffer = [];
     this.done = false;
   }
 
@@ -726,12 +728,20 @@ class RowIterator implements AsyncIterableIterator<string> {
     }
   }
 
+  async lookForward(): Promise<IteratorResult<string | symbol>> {
+    const res = await this.onRequested();
+    this.buffer.push(res);
+    return res;
+  }
+
   async next(): Promise<IteratorResult<string>> {
     if (this.done) {
       return { done: true, value: null };
     }
 
-    const { done, value } = await this.onRequested();
+    const { done, value } = this.buffer.length > 0
+      ? this.buffer.shift() as IteratorResult<string | symbol>
+      : await this.onRequested();
 
     if (done || value === newLine) {
       this.done = true;
@@ -842,6 +852,10 @@ class CSVRowIteratorReader implements AsyncIterableIterator<RowIterator> {
     }
 
     this.rowIterator = new RowIterator(() => this.onRequested());
+    const nextCell = await this.rowIterator.lookForward();
+    if (this.done && nextCell.done) {
+      return { done: true, value: undefined };
+    }
 
     return { done: false, value: this.rowIterator };
   }

reader_test.ts

@@ -1,6 +1,7 @@
 import { concat } from "./deps.ts";
 import { assertEquals, assertRejects } from "./dev_deps.ts";
 import {
+  newLine,
   readCSV,
   readCSVObjects,
   readCSVRows,
@@ -262,6 +263,25 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: "readCSV ignores trailing empty lines",
+  async fn() {
+    const reader = new MyReader(`1,2,3
+
+a,b,c
+
+
+`);
+
+    const rows = await asyncArrayFrom2(readCSV(reader));
+
+    assertEquals(rows, [
+      ["1", "2", "3"],
+      ["a", "b", "c"],
+    ]);
+  },
+});
+
 Deno.test({
   name: "readCSVStream couldn't be used twice",
   async fn() {
@@ -283,6 +303,22 @@ Deno.test({
   },
 });
 
+Deno.test({
+  name: "readCSVStream ignores trailing empty lines",
+  async fn() {
+    const reader = new MyReader(`1,2,3
+
+a,b,c
+
+
+`);
+
+    const rows = await asyncArrayFrom(readCSVStream(reader));
+
+    assertEquals(rows, ["1", "2", "3", newLine, "a", "b", "c", newLine]);
+  },
+});
+
 Deno.test({
   name: "readCSVRows couldn't be used twice",
   async fn() {
@@ -440,3 +476,22 @@ d,e,f`,
     ]);
   },
 });
+
+Deno.test({
+  name: "readCSVRows ignores trailing empty lines",
+  async fn() {
+    const reader = new MyReader(`1,2,3
+
+a,b,c
+
+
+`);
+
+    const rows = await asyncArrayFrom(readCSVRows(reader));
+
+    assertEquals(rows, [
+      ["1", "2", "3"],
+      ["a", "b", "c"],
+    ]);
+  },
+});