feat(manifest): drop unimplemented json sidecar store (V-L2-F2, #112) (#144)

Drop the never-implemented `json` sidecar store (V-L2-F2). The octad data
layer is intrinsically relational, so `json` is removed from the storage
enum, docs, template, and validate/doctor messaging rather than built.

Closes #112

Author: hyperpolymath

src/abi/mod.rs

@@ -460,7 +460,7 @@ impl AccessPolicy {
 /// with validation and path resolution.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SidecarConfig {
-    /// Storage backend: "sqlite" or "json".
+    /// Storage backend: "sqlite" (default) or "postgres"/"postgresql".
     pub storage: String,
     /// File path for the sidecar database.
     pub path: String,

src/codegen/overlay.rs

@@ -74,30 +74,35 @@ fn must_validate_identifier(name: &str) -> &str {
 /// genuinely dialect-divergent fragment is the metadata upsert
 /// (`INSERT OR IGNORE` vs `INSERT … ON CONFLICT DO NOTHING`), which lives
 /// in the [`sqlite`] / [`postgres`] modules.
+///
+/// [`from_storage`](SqlDialect::from_storage) is the single source of
+/// truth for which `[sidecar].storage` values are accepted; `generate`,
+/// `validate`, and `doctor` all defer to it.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum SqlDialect {
     Sqlite,
     Postgres,
 }
 
 impl SqlDialect {
-    /// Map a `[sidecar].storage` value to a dialect. `sqlite` →
-    /// [`SqlDialect::Sqlite`]; `postgres`/`postgresql` →
-    /// [`SqlDialect::Postgres`]. `json` and unknown values are rejected
-    /// (the previous behaviour silently emitted SQLite DDL regardless,
-    /// V-L2-F1). The JSON store is tracked separately by #112.
+    /// Map a `[sidecar].storage` value to a dialect (case-insensitive):
+    /// `sqlite` → [`SqlDialect::Sqlite`]; `postgres`/`postgresql` →
+    /// [`SqlDialect::Postgres`]. Every other value is rejected rather than
+    /// silently emitting SQLite DDL regardless of the backend (V-L2-F1).
+    ///
+    /// The octad data layer is intrinsically relational (hash-chains under
+    /// `BEGIN IMMEDIATE`, partial-unique temporal indexes, `CHECK`
+    /// constraints, recursive-CTE lineage acyclicity), so the
+    /// never-implemented `json` document store was dropped rather than
+    /// built (V-L2-F2, #112). It is now an unsupported value like any
+    /// other — no special-casing, no "coming soon" pointer.
     pub fn from_storage(storage: &str) -> anyhow::Result<Self> {
         match storage.to_lowercase().as_str() {
             "sqlite" => Ok(SqlDialect::Sqlite),
             "postgres" | "postgresql" => Ok(SqlDialect::Postgres),
-            "json" => anyhow::bail!(
-                "[sidecar].storage = \"json\" is not implemented (it previously \
-                 emitted SQLite DDL silently). Use \"sqlite\". The JSON sidecar \
-                 store is tracked by hyperpolymath/verisimiser#112."
-            ),
             other => anyhow::bail!(
-                "unknown [sidecar].storage {other:?}; supported: \"sqlite\" \
-                 (\"postgres\" for a PostgreSQL sidecar; \"json\" is #112)."
+                "unsupported [sidecar].storage {other:?}; supported values are \
+                 \"sqlite\" (default) and \"postgres\"/\"postgresql\"."
             ),
         }
     }
@@ -879,10 +884,18 @@ mod tests {
             SqlDialect::from_storage("PostgreSQL").unwrap(),
             SqlDialect::Postgres
         );
+        // V-L2-F2 (#112): the json store was dropped, never implemented. It
+        // is now rejected like any other unsupported value, and the error
+        // advertises only the supported stores — it must NOT imply json is
+        // planned (no "#112" / "not implemented" pointer).
         let json_err = SqlDialect::from_storage("json").unwrap_err().to_string();
         assert!(
-            json_err.contains("not implemented") && json_err.contains("#112"),
-            "json must be rejected with the #112 pointer, got: {json_err}"
+            json_err.contains("unsupported") && json_err.contains("sqlite"),
+            "json must be rejected as an unsupported store, got: {json_err}"
+        );
+        assert!(
+            !json_err.contains("#112") && !json_err.to_lowercase().contains("not implemented"),
+            "the dropped json store must not be advertised as planned, got: {json_err}"
         );
         assert!(SqlDialect::from_storage("mariadb").is_err());
     }

src/main.rs

@@ -209,9 +209,9 @@ fn main() -> Result<()> {
             // Create output directory.
             std::fs::create_dir_all(&output)?;
 
-            // The sidecar DDL dialect follows [sidecar].storage. This
-            // rejects `json` (tracked by #112) instead of silently
-            // emitting SQLite DDL for a non-SQLite store (V-L2-F1).
+            // The sidecar DDL dialect follows [sidecar].storage. Any value
+            // other than sqlite/postgres is rejected here (V-L2-F1) instead
+            // of silently emitting SQLite DDL for a non-SQLite store.
             let dialect = codegen::overlay::SqlDialect::from_storage(&m.sidecar.storage)?;
 
             // Generate sidecar overlay schema. Errors here surface invalid

src/manifest/mod.rs

@@ -279,11 +279,11 @@ mod octad_tests {
 /// temporal versions, and access policies. It never writes to your target database.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SidecarConfig {
-    /// Storage backend for the sidecar. `"sqlite"` (default) is the only
-    /// implemented store; `"postgres"`/`"postgresql"` selects the
-    /// PostgreSQL DDL dialect. `"json"` is **not implemented** and is
-    /// rejected at `generate` time — tracked by #112 (V-L2-F2). The
-    /// dialect mapping lives in `codegen::overlay::SqlDialect`.
+    /// Storage backend for the sidecar. `"sqlite"` (default) is the
+    /// reference store; `"postgres"`/`"postgresql"` selects the PostgreSQL
+    /// DDL dialect. Any other value is rejected at `validate` and
+    /// `generate` time by `codegen::overlay::SqlDialect::from_storage`,
+    /// the single source of truth for supported stores.
     #[serde(default = "default_sidecar_storage")]
     pub storage: String,
 
@@ -394,6 +394,41 @@ mod validate_manifest_tests {
         assert_eq!(failed, vec!["schema-source-exists"]);
     }
 
+    /// An unsupported `[sidecar].storage` (here the dropped `json` store,
+    /// V-L2-F2 / #112) must fail `sidecar-storage-supported`, and the
+    /// failure detail must not advertise json as a planned option.
+    #[test]
+    fn unsupported_storage_fails() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let path = dir.path().join("verisimiser.toml");
+        let sidecar_path = dir.path().join("sidecar.db");
+        let body = format!(
+            "[project]\n\
+             name = \"test\"\n\
+             [database]\n\
+             backend = \"sqlite\"\n\
+             [sidecar]\n\
+             storage = \"json\"\n\
+             path = \"{}\"\n",
+            sidecar_path.display().to_string().replace('\\', "/")
+        );
+        std::fs::write(&path, body).expect("write");
+
+        let report = validate_manifest(path.to_str().unwrap());
+        assert!(!report.passed);
+        let storage = report
+            .checks
+            .iter()
+            .find(|c| c.name == "sidecar-storage-supported")
+            .expect("storage check must run");
+        assert!(!storage.passed, "json storage must fail the check");
+        let detail = storage.detail.as_deref().unwrap_or_default();
+        assert!(
+            detail.contains("unsupported") && !detail.contains("#112"),
+            "detail must reject json plainly without a 'coming soon' pointer; got: {detail}"
+        );
+    }
+
     /// A malformed manifest must fail `manifest-loads` and stop further
     /// checks (because the rest depend on having a parsed manifest).
     #[test]
@@ -621,6 +656,7 @@ enable-constraints = {enable_constraints}
 enable-simulation = {enable_simulation}
 
 [sidecar]
+# storage backend: "sqlite" (default) or "postgres"/"postgresql"
 storage = "{sidecar_storage}"
 path = "{sidecar_path}"
 
@@ -734,6 +770,9 @@ impl ValidationReport {
 ///    set, the file at that path is readable.
 /// 3. **`sidecar-path-writable`** — the parent directory of
 ///    `[sidecar].path` is writable (or createable).
+/// 4. **`sidecar-storage-supported`** — `[sidecar].storage` names a
+///    backend `codegen` can emit (`sqlite`/`postgres`). Catches typos and
+///    the dropped `json` store (V-L2-F2 / #112).
 ///
 /// Out of scope here: V-L2-E1 backend/target_db conflict (own issue),
 /// target-DB reachability (needs live connection).
@@ -820,6 +859,28 @@ pub fn validate_manifest(path: &str) -> ValidationReport {
                 )),
             });
         }
+
+        // 4. Sidecar storage backend is supported. Delegates to the one
+        // validator (`SqlDialect::from_storage`) so `validate`/`doctor`
+        // and `generate` agree on the accepted set. This is where a typo'd
+        // or dropped backend (e.g. the never-implemented `json` store,
+        // V-L2-F2 / #112) is surfaced before it reaches codegen.
+        let storage_check = ValidationCheck {
+            name: "sidecar-storage-supported".to_string(),
+            description: "[sidecar].storage names a supported backend".to_string(),
+            passed: true,
+            detail: None,
+        };
+        checks.push(
+            match crate::codegen::overlay::SqlDialect::from_storage(&m.sidecar.storage) {
+                Ok(_) => storage_check,
+                Err(e) => ValidationCheck {
+                    passed: false,
+                    detail: Some(e.to_string()),
+                    ..storage_check
+                },
+            },
+        );
     }
 
     let passed = checks.iter().all(|c| c.passed);