Document the canonical Debug fingerprint and its evidence (improvise-djcn)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze
2026-09-23 08:47:21 -07:00
parent 6096c03caa
commit 47bab86a50
2 changed files with 46 additions and 0 deletions
@@ -512,6 +512,30 @@ change. `recomputing_formulas_leaves_the_model_fingerprint_alone` pins this.
 `view_only_effects_leave_shared_state_alone` now runs over a formula-bearing
 fixture, for the same reason.
 **That fix was canonical within one instance, not across two (improvise-djcn).**
 It fixed `Model`'s own maps but not the maps inside its fields. `DataStore` has
 `index`, `records` and the symbol table, and `View` has `page_selections`,
 `hidden_items` and `collapsed_groups`. All still printed through a derived
 `Debug`, in hash order. Each `HashMap` gets its own `RandomState`, so two equal
 documents built separately printed differently in 32 of 32 runs.
 - The effect-classification tests compare one instance with itself before and
  after, so they were unaffected.
 - `a_model_command_lands_where_its_keypress_lands` compares **two** `App`s. It
  passed only because its fixture had no cells and no multi-entry view maps.
 Now:
 - `DataStore`, `SymbolTable` and `View` have hand-written `Debug` impls. Each
  sorts wherever its storage is a hash map.
 - `DataStore` resolves symbols to their strings. A `Symbol`'s number is interning
  order, not content, so printing it would make two equal stores differ again.
 - `SymbolTable` prints its interned strings, sorted.
 - `cells` keeps its `IndexMap` order, because that order is part of the document
  (gotcha 18).
 - Every hand-written `Debug`, `Model`'s included, **destructures** `self`. A field
  added later is then a compile error there, where a `debug_struct` that names
  fields one by one would skip it silently. The pc3b version of `Model`'s impl
  had exactly that hole.
 `parse_number_cell` returns `CellValue::Error` naming the offending text rather
 than a fabricated `0.0`. No token the current grammar admits actually fails
 `f64::from_str` (overflow saturates to ±inf), but if the two ever drift the
@@ -205,6 +205,28 @@ Row, swapping the axes and rotating Row→Column land on the same view, and an
 equivalence test that cannot distinguish the wrong effect from the right one
 proves nothing (`doctrine(check_the_checker)`).
 **The fixture needs cells and multi-entry view maps too (improvise-djcn).** The
 test compares `format!("{:?}", workbook)` across **two** `App`s. It passed only
 because the fixture had no cells and every view map had at most one entry, and a
 `HashMap` of one entry has only one order. The fixture now carries:
 - three cells;
 - two page selections;
 - two categories with hidden items, one of them with two;
 - two categories with collapsed groups.
 That fixture was red in 3 of 3 runs on the old `Debug` impls: the by-key and
 by-command fingerprints differed only in hash order. It was green after the fix.
 Each half of the fix was checked by restoring the derived `Debug` on its own:
 - `View`'s derived `Debug` alone: 3 of 3 runs red.
 - `DataStore` and `SymbolTable`'s derived `Debug` alone: 3 of 3 runs red.
 So neither half is carried by the other. The exhaustive destructure in `Model`'s
 `Debug` has no test of its own, because it is a compile-time guard. It was
 checked by adding a `probe_field` to `Model` and to `Model::new`. The build then
 failed with `E0027: pattern does not mention field probe_field` at the `Debug`
 impl, and nowhere else.
 ### a_stale_wire_model_command_cannot_be_applied
 A wire `Command::Model` cannot reach the document without its basis being checked