[fhgffy]

With fieldsPerRecord: 0 the field count is taken from the first record the parser sees, even when that record is a blank line or a comment that ends up being skipped. The count becomes 0 and the first real row then fails:

parse("\na,b\nc,d", { fieldsPerRecord: 0 });
// SyntaxError: Syntax error on line 2: expected 0 fields but got 2

parse("# note\na,b\nc,d", { comment: "#", fieldsPerRecord: 0 });
// SyntaxError: Syntax error on line 2: expected 0 fields but got 2

CsvParseStream already skips blank lines, but a leading comment line has the same problem there, and with skipFirstRow: true the comment line is taken as the (empty) header:

ReadableStream.from(["# note\na,b\nc,d"])
  .pipeThrough(new CsvParseStream({ comment: "#", skipFirstRow: true }));
// SyntaxError: Syntax error on line 2: The record has 2 fields, but the header has 0 fields

parse() now infers the count from the first non-empty record, and CsvParseStream skips comment lines before the first-row handling. Both examples above now give [["a", "b"], ["c", "d"]] and [{ a: "c", b: "d" }], which matches Go's encoding/csv.

Added test cases to parse_test.ts and parse_stream_test.ts; they fail without the change. deno test -A csv/, deno lint csv/ and deno fmt --check csv/ pass.

[CLAassistant]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.03%. Comparing base (f834d02) to head (142f0c7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7352      +/-   ##
==========================================
- Coverage   95.04%   95.03%   -0.01%     
==========================================
  Files         619      619              
  Lines       52012    52012              
  Branches     9450     9448       -2     
==========================================
- Hits        49434    49431       -3     
- Misses       2031     2033       +2     
- Partials      547      548       +1     

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