Miscounting lines with mismatched columns (csv-core)

[etylermoss]

Example:

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=b2865b0972382499147f9f8e9eb43e84

Output:

line: 2, fields: ABC
line: 3, fields: a1b1c1
line: 4, fields: a2
line: 4, fields: a3b3c3d3

Expected (& should it not start from line 1?):

line: 2, fields: ABC
line: 3, fields: a1b1c1
line: 4, fields: a2
line: 5, fields: a3b3c3d3

[Rafferty97]

@etylermoss

I tried tweaking your demo such that all lines had the same number of columns, i.e.:

let data = "A,B,C\na1,b1,c1\na2,b2,c2\na3,b3,c3";

It produced the same results:

line: 2, fields: ABC
line: 3, fields: a1b1c1
line: 4, fields: a2b2c2
line: 4, fields: a3b3c3

My suspicion is that the call to reader.line() is returning the line it's about to parse, as it's already processed the \n by the time you get the record back, with the exception of the last line as it doesn't end in a \n character.

Indeed, if I run the exact same code but just add a \n character to the end of the input, I get these results instead:

line: 2, fields: ABC
line: 3, fields: a1b1c1
line: 4, fields: a2b2c2
line: 5, fields: a3b3c3

I think it's safe to call this one case closed :)