`libfec fastfec` crashes on form types containing `/` (e.g. SC/10)

[asg017]

Note

Much of this ticket was composed with Claude

When a filing contains a form type with a / character (e.g. SC/10), libfec fastfec crashes with "No such file or directory (os error 2)". The form type is used directly as a filename (SC/10.csv), which the OS interprets as a path with directory SC/ and file 10.csv. Since the SC/ directory doesn't exist, File::create_new fails.

FastFEC handles this correctly by replacing / with - in filenames (producing SC-10.csv).

Root Cause

fastfec.rs:96:

let f = File::create_new(filing_directory.join(format!("{}.csv", r.row_type)))?;

r.row_type is used unsanitized as a filename component. FEC form types like SC/10, SC/9, SC/10-A contain slashes that are path separators on Unix.

Affected Filing

Filing ID: 1937483 (3KB, F3N filing for LOGAN CUNNINGHAM FOR CONGRESS)

Reproduction

# libfec crashes:
libfec fastfec ~/.cache/libfec/cache/1937483.fec /tmp/out_libfec
# error: No such file or directory (os error 2)

# FastFEC succeeds:
fastfec --no-stdin ~/.cache/libfec/cache/1937483.fec /tmp/out_fastfec
# Done; parsing successful!

Observe the Difference

# libfec creates these files (missing SC/10):
ls /tmp/out_libfec/1937483/
# F3N.csv  SA11AI.csv  SA11D.csv  SA13A.csv  SB17.csv  header.csv

# FastFEC creates these files (includes SC-10):
ls /tmp/out_fastfec/1937483/
# F3N.csv  SA11AI.csv  SA11D.csv  SA13A.csv  SB17.csv  SC-10.csv  header.csv

# Diff the file lists:
diff <(ls /tmp/out_libfec/1937483/) <(ls /tmp/out_fastfec/1937483/)
# > SC-10.csv

Suggested Fix

Sanitize r.row_type before using as a filename, replacing / with - to match FastFEC behavior.