pdftract/notes/pdftract-5t92.md

pdftract-5t92: AcroForm Value Extraction for Tx/Btn/Ch Types

Summary

Completed Phase 7.4.2: AcroForm value extraction for Tx / Btn / Ch field types. The implementation was already present in the codebase - this task involved fixing two test failures and verifying complete functionality.

Work Done

Bug Fixes

1. Fixed test_extract_combo_with_multi_select_flag (value_choice.rs:473-491)

   • Problem: When both Combo and MultiSelect flags were set (malformed but possible), the code returned ChoiceValue::Multiple instead of ChoiceValue::Single(Some(_)).
   • Root Cause: extract_selected_value was called with is_multi_select=true for all fields, but combo boxes are always single-select regardless of the multi-select flag.
   • Fix: Modified extract_choice_value to pass is_multi_select && !is_combo to extract_selected_value calls (line 199-205).

2. Fixed test_extract_default_none_becomes_none (value_choice.rs:626-637)

   • Problem: Empty string defaults (Single(Some(""))) were being filtered out because is_empty() returns true for empty strings.
   • Root Cause: The filter default_val.filter(|v| !v.is_empty()) treated Single(Some("")) as empty and removed it.
   • Semantics: An explicit empty string default is different from no default at all. /DV "" means "default to empty" vs no /DV meaning "no default specified".
   • Fix: Added new is_truly_empty() method that only returns true for Single(None) and empty Multiple, not for Single(Some("")). Changed filter to use is_truly_empty() instead of is_empty() (line 210).

Verification

All acceptance criteria from the plan are met:

Criterion	Status	Notes
Critical test (text, checkbox, dropdown)	PASS	test_extract_values_tx_btn_ch_critical passes
Unit test: unselected checkbox	PASS	test_extract_values_unselected_checkbox passes
Unit test: selected radio	PASS	test_extract_values_selected_radio passes
Unit test: multi-select list	PASS	test_extract_values_multi_select_list passes
Unit test: combo with /Opt 2-tuple entries	PASS	test_extract_values_combo_with_opt_tuples passes
Unit test: multi-line text	PASS	test_extract_values_multiline_text passes
Public API extract_values function	PASS	pub fn extract_values(fields: &[AcroFormField]) -> Vec<(String, FormFieldValue)> exists
Sig fields are skipped	PASS	test_extract_values_skips_sig_fields passes
All /Ff bits preserved	PASS	FormFieldValue variants preserve all flags via multiline, pushbutton, radio, is_combo, is_multi_select fields

Implementation Details

The implementation consists of:

1. forms/mod.rs: Main entry point extract_values() and acro_field_to_value() - converts AcroFormField to FormFieldValue.
2. forms/value_text.rs: Text field extraction with PDFDocEncoding/UTF-16BE BOM decoding via decode_pdf_string().
3. forms/value_button.rs: Button field extraction distinguishing pushbutton, checkbox, and radio button types via /Ff flags.
4. forms/value_choice.rs: Choice field extraction for combo/list boxes with single/multi-select support.
5. forms/combiner.rs: FormFieldValue enum definition for type-safe values.

Files Modified

• crates/pdftract-core/src/forms/value_choice.rs: Fixed multi-select flag handling for combo boxes and empty string default filtering.

Test Results

test result: ok. 96 passed; 0 failed

All forms module tests pass:

• 16 tests in forms::tests (main module)
• 27 tests in forms::value_text::tests
• 31 tests in forms::value_button::tests
• 22 tests in forms::value_choice::tests

References

• Plan section 7.4 lines 2610-2613 (Tx/Btn/Ch)
• PDF 1.7 spec 12.7.4.2 (Tx), 12.7.4.3 (Btn), 12.7.4.4 (Ch)
• Phase 1 PdfString decoder (reused for text decoding)
• Phase 7.4.1 (input walker - provides AcroFormField)
• Phase 7.4.4 (combiner consumer - uses FormFieldValue)