M6: clearing a field's default leaves it with none, not its parent field's

/DV is inheritable (ISO 32000-2 §12.7.4.1). set_props removed a cleared
/DV, which brought back a parent field's, so Reset Form restored the
parent's default. When an ancestor sets /DV, a cleared default is now
written empty (/Off for buttons, () otherwise); with none it is removed
as before. New tree::ancestor_sets, cycle-safe and capped.

Adapted from pdfcer (MIT, same author) 6af2773ccf599b416fab379673119c6b37c55a2c.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SqmHYx8FiWM5PcsoiErgp9

crates/automation/tests/it/automation.rs

@@ -9175,3 +9175,28 @@ fn page_render_draws_stamps_without_an_appearance() {
     let grey = custom.iter().filter(|p| p[0].abs_diff(p[1]) < 24 && p[1].abs_diff(p[2]) < 24).count();
     assert!(grey > 100 && grey == custom.len(), "an unknown name is a grey placeholder: {grey} of {}", custom.len());
 }
+
+/// Clearing a field's default through `form_set_props` (`"default": ""`) leaves it with none,
+/// even when its parent field has one it would otherwise inherit.
+#[test]
+fn clearing_a_kids_default_through_tools_does_not_bring_back_its_parents() {
+    let objs = [
+        "<< /Type /Catalog /Pages 2 0 R /AcroForm 4 0 R >>",
+        "<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 400 300] >>",
+        "<< /Type /Page /Parent 2 0 R /Annots [6 0 R] >>",
+        "<< /Fields [5 0 R] /DA (/Helv 12 Tf 0 g) /DR << /Font << /Helv 7 0 R >> >> >>",
+        "<< /T (address) /FT /Tx /DV (Main St) /Kids [6 0 R] >>",
+        "<< /Type /Annot /Subtype /Widget /T (city) /Parent 5 0 R /DV (Elm) /V (Elm) /Rect [10 250 150 268] /P 3 0 R >>",
+        "<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica /Encoding /WinAnsiEncoding >>",
+    ];
+    let dir = workdir("kid-default");
+    std::fs::write(dir.join("form.pdf"), pdf_of(&objs)).unwrap();
+    let mut a = auto(&dir);
+    let doc = ok(&mut a, "doc_open", json!({ "path": "form.pdf" }))["doc"].as_u64().unwrap();
+    ok(&mut a, "form_set_props", json!({ "doc": doc, "field": "address.city", "default": "" }));
+    ok(&mut a, "form_fill", json!({ "doc": doc, "values": { "address.city": "Oak" } }));
+    ok(&mut a, "form_reset", json!({ "doc": doc }));
+    let fields = ok(&mut a, "form_fields", json!({ "doc": doc }));
+    let city = fields["fields"].as_array().unwrap().iter().find(|f| f["name"] == "address.city").unwrap().clone();
+    assert!(city["value"].is_null() || city["value"] == "", "reset clears it rather than restoring the parent's Main St: {}", city["value"]);
+}

crates/forms/src/author/edit.rs

@@ -1,5 +1,5 @@
 use super::look::{BorderStyle, da_string, patch_da, patch_widget_look, redraw_widgets};
-use super::tree::{attach, check_place, child_named, clash, detach, ensure_form, inherited, name_parts, own_inherited};
+use super::tree::{ancestor_sets, attach, check_place, child_named, clash, detach, ensure_form, inherited, name_parts, own_inherited};
 use super::*;
 
 /// Swap width and height, keeping the center. `None` when that is not a usable widget.
@@ -173,6 +173,7 @@ pub fn set_props(doc: &mut Document, name: &str, props: &FieldProps) -> Result<S
     if props.check_style.is_some() && !matches!(f.kind, FieldKind::CheckBox | FieldKind::Radio) {
         return invalid("only check boxes and radio buttons have a check style");
     }
+    let parent_default = ancestor_sets(doc, f.obj, b"DV");
     doc.update_dict(f.obj, |d| {
         d.set(b"Ff".to_vec(), Object::Int(ff as i64));
         if let Some(t) = &props.tooltip {
@@ -219,6 +220,12 @@ pub fn set_props(doc: &mut Document, name: &str, props: &FieldProps) -> Result<S
             // Buttons name their default state; text and choices hold a string.
             Some(Some(v)) if matches!(f.kind, FieldKind::CheckBox | FieldKind::Radio) => d.set(b"DV".to_vec(), Object::Name(crate::name_bytes(v))),
             Some(Some(v)) => d.set(b"DV".to_vec(), PdfString::text(v)),
+            // `/DV` is inheritable: with an ancestor's in place, removing the field's own would
+            // bring that one back, so the field keeps an empty default of its own instead.
+            Some(None) if parent_default && matches!(f.kind, FieldKind::CheckBox | FieldKind::Radio) => {
+                d.set(b"DV".to_vec(), Object::Name(b"Off".to_vec()))
+            }
+            Some(None) if parent_default => d.set(b"DV".to_vec(), PdfString::text("")),
             Some(None) => {
                 d.remove(b"DV");
             }

crates/forms/src/author/tree.rs

@@ -317,6 +317,24 @@ pub(super) fn inherited(doc: &Document, field: ObjRef) -> Dict {
     add
 }
 
+/// Whether an ancestor of `field` sets the inheritable `key`, which `field` would take on without
+/// its own entry.
+pub(super) fn ancestor_sets(doc: &Document, field: ObjRef, key: &[u8]) -> bool {
+    let mut seen = std::collections::HashSet::new();
+    let mut parent = doc.get(field).as_dict().and_then(|d| d.reference(b"Parent"));
+    while let Some(p) = parent {
+        if seen.len() > 64 || !seen.insert(p) {
+            return false;
+        }
+        let Some(d) = doc.get(p).as_dict().cloned() else { return false };
+        if d.contains(key) {
+            return true;
+        }
+        parent = d.reference(b"Parent");
+    }
+    false
+}
+
 /// Copy onto `field` what it inherits (`add`, from [`inherited`]), so it keeps it when it moves.
 pub(super) fn own_inherited(doc: &mut Document, field: ObjRef, add: &Dict) -> Result<(), FormError> {
     if add.iter().next().is_some() {

crates/forms/src/tests.rs

@@ -4577,3 +4577,57 @@ fn set_values_reads_the_form_once_not_per_value() {
     let reads = form_reads() - before;
     assert_eq!(reads, 3, "one to fill, one when f0 comes again, one to recalculate");
 }
+
+#[test]
+fn clearing_a_kids_default_does_not_bring_back_its_parents() {
+    let mut doc = fixture();
+    let all = fields(&doc);
+    let city = field(&all, "address.city").clone();
+    let parent = doc.get(city.obj).as_dict().unwrap().reference(b"Parent").unwrap();
+    doc.update_dict(parent, |d| d.set(b"DV".to_vec(), PdfString::text("Main St"))).unwrap();
+    set_props(&mut doc, "address.city", &FieldProps { default_value: Some(Some("Elm".into())), ..FieldProps::default() }).unwrap();
+    assert_eq!(field(&fields(&doc), "address.city").default, ["Elm"]);
+    set_props(&mut doc, "address.city", &FieldProps { default_value: Some(None), ..FieldProps::default() }).unwrap();
+    let mut doc = reopen(&doc);
+    let f = field(&fields(&doc), "address.city").clone();
+    assert!(f.default.iter().all(String::is_empty), "no default, not the parent's: {:?}", f.default);
+    let own = doc.get(f.obj).as_dict().and_then(|d| d.get(b"DV")).and_then(|o| o.as_string()).map(PdfString::to_text);
+    assert_eq!(own.as_deref(), Some(""), "the kid holds an empty default of its own");
+    set_value(&mut doc, "address.city", &FieldValue::Text("Oak".into())).unwrap();
+    reset(&mut doc, None).unwrap();
+    assert!(field(&fields(&doc), "address.city").value.iter().all(String::is_empty), "reset clears it");
+    // Without a parent default, clearing still removes the key.
+    set_props(&mut doc, "name", &FieldProps { default_value: Some(None), ..FieldProps::default() }).unwrap();
+    let name = field(&fields(&doc), "name").clone();
+    assert!(doc.get(name.obj).as_dict().unwrap().get(b"DV").is_none());
+}
+
+#[test]
+fn clearing_a_buttons_default_under_a_parent_with_one_leaves_it_off() {
+    // A check box, then a radio button (flags 49152, inherited from the parent).
+    for flags in ["", "/Ff 49152"] {
+        let mut doc = document(&[
+            "<< /Type /Catalog /Pages 2 0 R /AcroForm 4 0 R >>".into(),
+            "<< /Type /Pages /Kids [3 0 R] /Count 1 /MediaBox [0 0 600 800] >>".into(),
+            "<< /Type /Page /Parent 2 0 R /Annots [6 0 R] >>".into(),
+            "<< /Fields [5 0 R] /DA (/Helv 0 Tf 0 g) >>".into(),
+            format!("<< /T (opts) /FT /Btn {flags} /DV /Yes /Kids [6 0 R] >>"),
+            "<< /Type /Annot /Subtype /Widget /T (a) /Parent 5 0 R /V /Off /AS /Off /Rect [10 10 25 25] /P 3 0 R /AP << /N << /Yes 7 0 R /Off 7 0 R >> >> >>".into(),
+            "<< /Length 0 >>
+stream
+
+endstream".into(),
+        ]);
+        let kind = field(&fields(&doc), "opts.a").kind;
+        assert_eq!(kind == FieldKind::Radio, !flags.is_empty());
+        set_props(&mut doc, "opts.a", &FieldProps { default_value: Some(None), ..FieldProps::default() }).unwrap();
+        let f = field(&fields(&doc), "opts.a").clone();
+        assert_eq!(doc.get(f.obj).as_dict().and_then(|d| d.get(b"DV")).and_then(|o| o.as_name()), Some(&b"Off"[..]), "{kind:?}");
+        let on = if kind == FieldKind::Radio { FieldValue::Radio(Some("Yes".into())) } else { FieldValue::Check(true) };
+        set_value(&mut doc, "opts.a", &on).unwrap();
+        assert_eq!(field(&fields(&doc), "opts.a").value, ["Yes"]);
+        reset(&mut doc, None).unwrap();
+        let f = field(&fields(&doc), "opts.a").clone();
+        assert!(f.value.iter().all(String::is_empty), "{kind:?}: reset leaves it off, not the parent's Yes: {:?}", f.value);
+    }
+}

parity/acrobat-features.toml

@@ -4991,8 +4991,8 @@ milestone = "M6"
 status = "shipped"
 commands = ["form.field.properties"]
 tools = ["form_set_props"]
-evidence = ["crates/forms/src/tests.rs::button_caption_preserves_other_widgets_and_shared_dictionaries", "crates/forms/src/tests.rs::a_button_caption_is_drawn_in_its_fields_font_size_and_color", "crates/ui-egui/tests/it/prepare.rs::button_label_is_editable_without_renaming_the_field", "crates/automation/tests/it/button_caption.rs::button_caption_can_be_changed_after_creation", "crates/forms/src/tests.rs::properties_rename_and_delete", "crates/automation/tests/it/automation.rs::preparing_a_form_through_tools", "crates/forms/src/tests.rs::options_tab_flags_alignment_and_defaults", "crates/ui-egui/tests/it/prepare.rs::options_tab_sets_flags_alignment_and_defaults", "crates/automation/tests/it/form_bulk.rs::bulk_options_apply_per_field_and_refuse_an_invalid_comb_atomically"]
-notes = "push buttons: per-widget normal label independent of the field name, including clearing and save/reopen, drawn in the font, size and color of the button's /DA (the form's /DR font, else Helvetica; an automatic size fits the button) and centered by Helvetica's widths; icon-only layout retained, rollover/down labels and icon layout editing remain unavailable; text: alignment, default, multi-line, scroll, rich text flag, limit, password, file selection, spell check, comb; choices: items, default, sort, custom text, multiple selection, commit immediately; check boxes and radios: checked by default, radios in unison. Shared GUI offers applicable text/choice flags, alignment, text limits and check styles; choices/defaults remain individual GUI edits"
+evidence = ["crates/forms/src/tests.rs::button_caption_preserves_other_widgets_and_shared_dictionaries", "crates/forms/src/tests.rs::a_button_caption_is_drawn_in_its_fields_font_size_and_color", "crates/ui-egui/tests/it/prepare.rs::button_label_is_editable_without_renaming_the_field", "crates/automation/tests/it/button_caption.rs::button_caption_can_be_changed_after_creation", "crates/forms/src/tests.rs::properties_rename_and_delete", "crates/automation/tests/it/automation.rs::preparing_a_form_through_tools", "crates/forms/src/tests.rs::options_tab_flags_alignment_and_defaults", "crates/ui-egui/tests/it/prepare.rs::options_tab_sets_flags_alignment_and_defaults", "crates/automation/tests/it/form_bulk.rs::bulk_options_apply_per_field_and_refuse_an_invalid_comb_atomically", "crates/forms/src/tests.rs::clearing_a_kids_default_does_not_bring_back_its_parents", "crates/forms/src/tests.rs::clearing_a_buttons_default_under_a_parent_with_one_leaves_it_off", "crates/automation/tests/it/automation.rs::clearing_a_kids_default_through_tools_does_not_bring_back_its_parents"]
+notes = "push buttons: per-widget normal label independent of the field name, including clearing and save/reopen, drawn in the font, size and color of the button's /DA (the form's /DR font, else Helvetica; an automatic size fits the button) and centered by Helvetica's widths; icon-only layout retained, rollover/down labels and icon layout editing remain unavailable; text: alignment, default (clearing it leaves none, not a parent field's), multi-line, scroll, rich text flag, limit, password, file selection, spell check, comb; choices: items, default, sort, custom text, multiple selection, commit immediately; check boxes and radios: checked by default, radios in unison. Shared GUI offers applicable text/choice flags, alignment, text limits and check styles; choices/defaults remain individual GUI edits"
 
 [[feature]]
 id = "form.props-actions"