refactor(csv): remove dead code and improve tests (#5151)

csv/parse.ts

@@ -50,35 +50,29 @@ class Parser {
  #readLine(): string | null {
  if (this.#isEOF()) return null;
 
- if (
- !this.#input.startsWith("\r\n", this.#cursor) ||
- !this.#input.startsWith("\n", this.#cursor)
- ) {
- let buffer = "";
- let hadNewline = false;
- while (this.#cursor < this.#input.length) {
- if (this.#input.startsWith("\r\n", this.#cursor)) {
- hadNewline = true;
- this.#cursor += 2;
- break;
- }
- if (
- this.#input.startsWith("\n", this.#cursor)
- ) {
- hadNewline = true;
- this.#cursor += 1;
- break;
- }
- buffer += this.#input[this.#cursor];
- this.#cursor += 1;
+ let buffer = "";
+ let hadNewline = false;
+ while (this.#cursor < this.#input.length) {
+ if (this.#input.startsWith("\r\n", this.#cursor)) {
+ hadNewline = true;
+ this.#cursor += 2;
+ break;
  }
- if (!hadNewline && buffer.endsWith("\r")) {
- buffer = buffer.slice(0, -1);
+ if (
+ this.#input.startsWith("\n", this.#cursor)
+ ) {
+ hadNewline = true;
+ this.#cursor += 1;
+ break;
  }
-
- return buffer;
+ buffer += this.#input[this.#cursor];
+ this.#cursor += 1;
  }
- return null;
+ if (!hadNewline && buffer.endsWith("\r")) {
+ buffer = buffer.slice(0, -1);
+ }
+
+ return buffer;
  }
  #isEOF(): boolean {
  return this.#cursor >= this.#input.length;

csv/parse_test.ts

@@ -813,6 +813,24 @@ Deno.test({
  assertEquals(parse(input, { trimLeadingSpace: true }), output);
  },
  });
+ await t.step({
+ name: "leading line breaks",
+ fn() {
+ const input = "\n\na,b,c";
+ const output = [["a", "b", "c"]];
+ assertEquals(parse(input), output);
+ },
+ });
+ await t.step({
+ name: "throws when skipFirstRow=true with empty data",
+ fn() {
+ assertThrows(
+ () => parse("", { skipFirstRow: true }),
+ Error,
+ "Headers must be defined",
+ );
+ },
+ });
  },
 });