pdfcraft/docs/form-maxlen-compatibility.md

AcroForm /MaxLen 0 compatibility

Status: implemented; proposed as a separate compatibility PR. Last updated: 2026-10-19.

• crates/forms/src/lib.rs::walk reads inherited /MaxLen; the UI and value validation both consume Field::max_len.

The parser exposed /MaxLen 0 as Some(0), so both editor and API blocked input. It now exposes only positive limits; zero clears an inherited limit. The original object entry is preserved through save/reopen. This is an interoperability interpretation for zero, not a claim that ISO explicitly defines zero as unlimited. ISO 32000-1 Table 229 defines an optional inheritable maximum length without defining a special zero meaning: public specification. Positive limits remain enforced; no field names or character-sheet rules enter product code.

Regression: crates/forms/src/tests.rs::zero_max_len_is_unlimited_and_overrides_inherited_limit. The forms README and form.fill-text parity entry document this behavior.

Historical validation recorded before this review:

• Forms unit suite: all 68 tests passed. The new zero-limit regression was first run against the old parser and failed (Some(0) instead of None), then passed with the compatibility interpretation. Its positive-limit control and preserved raw entry also passed.

The user reports successful Class text input on the integrated release using their Pathfinder character sheet. This is a manual functional result, without timings; the private document was not used for automated regression tests in this review.

Independent branch validation

Validated on upstream a12fe8f4116984ebbc870eb514346ea922233316 with an isolated Cargo target directory and no performance changes:

• The focused regression failed with the original parser (Some(0) rather than None), then passed after restoring the compatibility fix.
• cargo test -p pdfcraft-forms -j 2: 81 unit tests passed; doc tests passed.
• cargo clippy -p pdfcraft-forms -j 2 --all-targets -- -D warnings: passed.
• cargo check --target wasm32-unknown-unknown -p pdfcraft-forms -j 2: passed.
• cargo fmt --check, git diff --check, and cargo xtask layers, assets, parity: passed.

These are local checks, not hosted CI. No private PDF was used.

Rebase validation

Rebased onto freshly fetched upstream main 932bf9c6bfdd63e2a21bb831696a3447b9def9cf on 2026-10-18. The only conflict was in the M6 roadmap row; upstream CSV/XML updates were retained alongside the compatibility note. The implementation and original regression are unchanged from the independent branch.

Validation used a fresh Cargo target directory, two build jobs, and locked, offline builds:

• The original regression failed with the upstream parser (Some(0) instead of None), then passed with the compatibility fix restored.
• Forms: 83 unit tests passed. Engine: 282 unit and 9 integration tests passed. JavaScript: 47 unit tests passed. Doc tests passed. The timing probe and two private-file tests remained ignored.
• The automation javascript_through_tools regression passed.
• Scoped Clippy for forms, engine and JavaScript, with --all-targets -- -D warnings, passed.
• WASM checks for those three crates passed.
• Rust formatting, whitespace, layering, assets and parity checks passed.
• A freshly built CLI filled synthetic fields with direct and inherited /MaxLen 0, rendered their values, saved/reopened them and accepted longer text after reopening. Its positive-limit control rejected six characters for /MaxLen 5; the synthetic input file stayed unchanged.

No performance optimizations, JavaScript snapshot/diff changes or profiling instrumentation are included. Existing executables, backups and private PDFs were not modified.

PR #3323 refresh

Revalidated against freshly fetched upstream main 4db6ac4ae2448df6389d8bb0bc54db6ba175721c on 2026-10-18. Conflicts in both roadmaps were resolved by keeping upstream's button-label and content-editing notes alongside the /MaxLen 0 documentation. The original compatibility implementation and regression are preserved; no performance changes were added to the PR.

Forms: 85 unit tests passed. Engine: 283 unit and 15 integration tests passed. JavaScript: 48 unit tests passed. The automation JavaScript regression, scoped Clippy with warnings denied, WASM, formatting, whitespace, layering, assets and parity checks all passed. The synthetic CLI fill/render/save/reopen and positive-limit control passed. The original regression again failed with the old parser and passed with the fix restored. Private-file tests remained ignored.

2026-10-19 revalidation

Rebased onto freshly fetched upstream main 459379ef9b127648cc30c0b2fe2b20c2b2375f04. Only ROADMAP.md required manual conflict resolution; all upstream entries and the compatibility note were retained. The implementation, original regression and forms README remain byte-for-byte identical to the previously reviewed compatibility head. No performance changes were introduced.

Validation used a fresh isolated build directory, two jobs, and locked offline builds:

• The original regression failed with the old parser and passed with the fix restored.
• Forms: 93 unit tests passed. Engine: 283 unit and 15 integration tests passed. JavaScript: 48 tests passed. Doc tests passed; the timing probe and two private-file tests remained ignored.
• Automation JavaScript, scoped all-targets Clippy with warnings denied, WASM, formatting, whitespace, layering, assets and parity passed.
• Synthetic CLI fill/render/save/reopen checks passed for direct zero and zero overriding an inherited positive limit. Longer text after reopening was accepted. The /MaxLen 5 control rejected six characters, and the synthetic input stayed unchanged.

These are local checks, not hosted CI. Existing executables, backups and private PDFs were not modified; only the compatibility worktree was changed.

Revision history

• 2026-10-19: refresh PR #3323 onto upstream 459379ef, retain all upstream roadmap entries and independently repeat regression, native/WASM, repository and CLI validation.

• 2026-10-18: refresh PR #3323 onto upstream 4db6ac4a, retaining both roadmap updates and independently revalidating compatibility and repository checks.

• 2026-10-18: rebase onto fetched upstream 932bf9c6; preserve upstream roadmap updates and independently revalidate the regression, forms/engine/JavaScript suites and quality gates.

• 2026-10-18: isolate the compatibility change on current upstream main; verify the regression before and after the fix, the forms suite and scoped quality gates.