P3: the books' format moves only with the owner's go-ahead (D-39)

Books an update could write a newer format for open on their old format
and are asked at every open; anything needing a new feature is refused
until the owner agrees with the passphrase, after a verified backup that
includes the keys. New books start on the current format. Each projection
schema has its own database file, so an older version still opens the
books until the owner agrees.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-mcp/tests/spec_party_totals.rs

@@ -361,7 +361,25 @@ const CHART: &[(&str, &str, &str)] = &[
 /// financing 2100; the chart; both members and the card's issuer in the
 /// directory.
 fn books(name: &str) -> Mcp {
+    books_in(name, false)
+}
+
+/// [`books`], as P2 left them when `p2`: journal format 2 with none of
+/// P3's features, books an older version wrote, waiting for their format
+/// upgrade (rules.md B-27).
+fn books_in(name: &str, p2: bool) -> Mcp {
     let dir = test_dir(name);
+    if p2 {
+        ledger_store::Store::create_in_format(
+            &dir.join("books-data"),
+            ledger_core::Currency::USD,
+            &ledger_store::JournalFormat {
+                format: 2,
+                features: Vec::new(),
+            },
+        )
+        .unwrap();
+    }
     let toml = books_toml(
         &dir,
         "Fernhill Labs LLC",
@@ -378,6 +396,25 @@ fn books(name: &str) -> Mcp {
     m
 }
 
+impl Mcp {
+    /// The owner's go-ahead, as the app gives it (ledger-gui owner.rs,
+    /// after the passphrase and a verified backup; no tool can): the
+    /// server stopped, the books moved to this version's format, and
+    /// served again.
+    fn upgraded(mut self) -> Mcp {
+        let dir = self.books_dir.take().expect("books_dir");
+        drop(self);
+        ledger_store::Store::open(&dir.join("books-data"))
+            .unwrap()
+            .upgrade_format()
+            .unwrap()
+            .expect("P2's books wait for the upgrade");
+        let mut m = Mcp::start(&dir, &dir.join("wanderbooks.toml"));
+        m.books_dir = Some(dir);
+        m
+    }
+}
+
 /// A party's part of an entry as books.get_entry gives it: (resolved,
 /// direction, cash, in_kind).
 fn part(m: &mut Mcp, entry: u64, party: &str) -> (Value, Value, Value, Value) {
@@ -560,7 +597,8 @@ fn defect14_party_totals_take_a_basis() {
 
 /// Defect 24 over the MCP: `books.update_party` `creditor_of` names the
 /// liabilities the company owes a party itself on (journaled as
-/// party.creditor_set, the journal's feature declared first), replaces
+/// party.creditor_set, under the journal feature the books declared when
+/// they were created, so nothing is declared on the way), replaces
 /// the list, refuses what isn't a liability with nothing journaled; and a
 /// fee on the issuer's own card then reads neither, so the issuer is paid
 /// what the card payment paid, once.
@@ -595,8 +633,8 @@ fn defect24_creditor_of_round_trips_and_a_card_fee_is_not_a_payment() {
     assert_eq!(m.count("party.creditor_set"), 1);
     assert_eq!(
         m.count("journal.format_set"),
-        before + 1,
-        "the feature declared once"
+        before,
+        "nothing declared on the way"
     );
     // The same list again changes nothing.
     let journal = m.journal();
@@ -633,31 +671,40 @@ fn defect24_creditor_of_round_trips_and_a_card_fee_is_not_a_payment() {
     );
     assert_eq!(p["creditor_of"], json!([]));
     assert_eq!(m.count("party.creditor_set"), 4);
-    assert_eq!(m.count("journal.format_set"), before + 1);
+    assert_eq!(m.count("journal.format_set"), before);
     let p = m.read_only("books.party", json!({"party": "Tobin Harlow"}));
     assert_eq!(p["party"]["creditor_of"], json!(["2100"]));
     assert_eq!(m.ok("books.verify", json!({}))["status"], "ok");
 }
 
-/// rules.md B-27: `books.update_party` declares the `party_creditors`
-/// feature before the first line it writes, never between them: a name
-/// change with the first creditor is journaled as the declaration, then
-/// the name, then the creditor (a refused format upgrade then leaves
-/// nothing half done).
+/// rules.md B-27: `books.update_party` asks for the `party_creditors`
+/// feature before the first line it writes, never between them. In books
+/// waiting for their format upgrade (P2's), a name change with the first
+/// creditor is refused whole, journaling nothing (never the notes changed
+/// and the creditor not); once the owner upgrades them, as in books this
+/// version made, it journals the change, then the creditor, and declares
+/// nothing.
 #[test]
-fn update_party_declares_the_creditor_feature_before_its_first_line() {
-    let mut m = books("feature-first");
-    let start = m.journal_types().len();
-    let p = m.ok(
-        "books.update_party",
-        json!({"party": "Harbor Bank", "notes": "the card's issuer", "creditor_of": ["2050"]}),
+fn update_party_asks_for_the_creditor_feature_before_its_first_line() {
+    let change =
+        json!({"party": "Harbor Bank", "notes": "the card's issuer", "creditor_of": ["2050"]});
+    let mut m = books_in("feature-first", true);
+    let why = m.refuse("books.update_party", change.clone());
+    assert!(
+        why.starts_with("format_upgrade_pending:") && why.contains("party_creditors"),
+        "{why}"
     );
-    assert_eq!(p["creditor_of"], json!(["2050"]));
-    assert_eq!(
-        m.journal_types()[start..].to_vec(),
-        ["journal.format_set", "party.updated", "party.creditor_set"],
-    );
-    assert_eq!(m.ok("books.verify", json!({}))["status"], "ok");
+    assert_eq!(m.count("party.updated"), 0, "nothing half done");
+    for mut m in [m.upgraded(), books("feature-first-new")] {
+        let start = m.journal_types().len();
+        let p = m.ok("books.update_party", change.clone());
+        assert_eq!(p["creditor_of"], json!(["2050"]));
+        assert_eq!(
+            m.journal_types()[start..].to_vec(),
+            ["party.updated", "party.creditor_set"],
+        );
+        assert_eq!(m.ok("books.verify", json!({}))["status"], "ok");
+    }
 }
 
 /// What `books.post_entry` previews is what it posts: each party's