Implement remote libSQL DDL support and refactor DDL builders

.tabularium

@@ -2,11 +2,13 @@
   "name": "libsql",
   "version": "0.1.0",
   "kind": "driver",
-  "description": "libSQL / Turso driver. Connects to local libSQL/SQLite files and to remote Turso or sqld servers over the Hrana HTTP protocol.",
+  "description": "libSQL / Turso driver. Connects to local libSQL/SQLite files (embedded libSQL fork: ALTER COLUMN and foreign-key add/drop work locally) and to remote Turso or sqld servers over the Hrana HTTP protocol.",
   "engine": "libsql",
   "paradigms": [
     "sql"
   ],
+  "icon": "sqlite",
+  "color": "#4ff8d2",
   "default_username": "",
   "executable": "libsql-plugin",
   "capabilities": {
@@ -16,14 +18,21 @@
     "file_based": false,
     "folder_based": false,
     "connection_string": true,
-    "connection_string_example": "libsql://my-db.turso.io?authToken=...  (or a local path like /data/app.db)",
+    "connection_string_example": "libsql://my-db.turso.io?authToken=...  (or a local file via file:///data/app.db)",
+    "connection_uri": true,
+    "connection_uri_schemes": [
+      "turso",
+      "wss",
+      "ws",
+      "file"
+    ],
     "identifier_quote": "\"",
     "alter_primary_key": false,
     "inline_pk": true,
     "auto_increment_keyword": "AUTOINCREMENT",
     "serial_type": "",
-    "alter_column": false,
-    "create_foreign_keys": false,
+    "alter_column": true,
+    "create_foreign_keys": true,
     "no_connection_required": false,
     "manage_tables": true,
     "readonly": false,

Cargo.toml

@@ -16,9 +16,14 @@ path = "src/main.rs"
 
 [dependencies]
 serde_json = "1"
-# Local file backend: bundled SQLite, compiled from source -> no system lib
-# needed, builds identically on Linux, macOS and Windows.
-rusqlite = { version = "0.31", features = ["bundled"] }
+# Local file backend: the libSQL fork of SQLite, bundled (compiled from source
+# -> no system lib, builds identically on Linux, macOS and Windows). Using the
+# fork gives local files the same ALTER COLUMN / FK-add extensions as remote
+# Turso servers. The `core` feature is embedded-local only; the async API does
+# all its work synchronously, so futures::executor::block_on bridges it
+# without pulling in a tokio runtime.
+libsql = { version = "0.9", default-features = false, features = ["core"] }
+futures = "0.3"
 # Remote backend: blocking HTTP client with pure-Rust rustls TLS (no OpenSSL),
 # used to speak the Hrana-over-HTTP pipeline protocol to Turso / sqld.
 ureq = { version = "2", features = ["json"] }

README.md

@@ -50,12 +50,41 @@ libsql://my-db.turso.io?authToken=eyJ...
 | Insert / update / delete rows (bound parameters) | ✅ |
 | Schema snapshot + batch columns/FKs (ER diagram) | ✅ |
 | `CREATE TABLE` SQL, add column, create/drop index | ✅ |
-| Schemas, stored routines | ❌ (not a SQLite concept) |
-| Alter column type, add/drop foreign key on existing table | ❌ (SQLite limitation — returns a clear error) |
+| Schemas, stored routines | ❌ (not a SQLite concept — Turso has no stored procedures, and its multi-database model is separate databases, not schemas) |
+| Rename column | ✅ everywhere (vanilla `RENAME COLUMN`) |
+| Alter column type / default | ✅ remote Turso/sqld (libSQL `ALTER COLUMN` extension) / ⚠️ local files — the host calls the SQL builder without connection params, so the libSQL statement is generated unconditionally and local SQLite rejects it with its own parse error when the host runs it |
+| Drop foreign key on existing table | ✅ remote Turso/sqld (has connection params) / ❌ local (clear error) |
+| Add foreign key to existing table | ❌ (protocol limitation — see below) |
 
 Identifiers are quoted ANSI-style (`"name"`). Booleans are stored as `0`/`1` and
 BLOBs are returned base64-encoded.
 
+### Turso-only schema changes
+
+Remote Turso / sqld servers run the **libSQL fork** of SQLite, which adds
+`ALTER TABLE ... ALTER COLUMN col TO col <type> [DEFAULT ...] [REFERENCES ...]`.
+The plugin uses it to:
+
+- change a column's type (and optionally its DEFAULT / NOT NULL),
+- drop a foreign key from an existing column (the same statement without the
+  `REFERENCES` clause).
+
+Local SQLite files cannot retype columns or touch existing foreign keys. The
+driver reports a clear error for foreign-key drops; note that libSQL applies
+constraint changes to newly inserted/updated rows only — existing rows are not
+rewritten or revalidated — and foreign key *enforcement* requires
+`PRAGMA foreign_keys=ON`.
+
+> **Why "add foreign key to existing table" is unavailable:** the host calls
+> the SQL preview builders with *no connection params*, and the libSQL
+> `ALTER COLUMN` rewrite replaces the column's whole definition — so building
+> the statement requires the column's declared type, which the host does not
+> send (only its name) and the plugin has no connection to look up. The
+> `.tabularium` capability is `create_foreign_keys: false`, so Tabularis hides
+> the add-FK dialog. Define foreign keys in the `CREATE TABLE` statement
+> instead. Dropping a foreign key does receive connection params and works on
+> remote Turso/sqld.
+
 ## Build & test
 
 Requires a Rust toolchain (and a C compiler for the bundled SQLite).
@@ -86,11 +115,16 @@ echo '{"jsonrpc":"2.0","method":"get_tables","params":{"params":{"database":"/tm
 ## Installing
 
 `just dev-install` copies `libsql-plugin` and `.tabularium` into the Tabularis
-plugins folder:
+plugins folder (the location Tabularis actually scans — derived from
+`ProjectDirs::from("com", "debba", "tabularis")`):
 
 - **Linux:** `~/.local/share/tabularis/plugins/libsql/`
-- **macOS:** `~/Library/Application Support/tabularis/plugins/libsql/`
-- **Windows:** `%APPDATA%\tabularis\plugins\libsql\`
+- **macOS:** `~/Library/Application Support/com.debba.tabularis/plugins/libsql/`
+- **Windows:** `%APPDATA%\debba\tabularis\data\plugins\libsql\`
+
+Note: the plugin guide's plain `%APPDATA%\tabularis\plugins` / macOS
+`tabularis/plugins` paths are wrong — that folder holds app config, not
+plugins; Tabularis scans the ProjectDirs path above.
 
 Restart Tabularis (or toggle the plugin in Settings) and **libSQL** appears in
 the Database Type list.

justfile

@@ -47,12 +47,7 @@ dev-install: build
 
 [windows]
 dev-install: build
-    $dest = Join-Path $env:APPDATA "tabularis\plugins\libsql"
-    New-Item -ItemType Directory -Force -Path $dest | Out-Null
-    Copy-Item "target\debug\libsql-plugin.exe" $dest
-    Copy-Item ".tabularium" $dest
-    Write-Host "Installed to $dest"
-    Write-Host "Restart Tabularis (or toggle the plugin in Settings) to pick up changes."
+    $dest = Join-Path $env:APPDATA "tabularis\plugins\libsql"; New-Item -ItemType Directory -Force -Path $dest | Out-Null; Copy-Item "target\debug\libsql-plugin.exe" $dest; Copy-Item ".tabularium" $dest; Write-Host "Installed to $dest"; Write-Host "Restart Tabularis (or toggle the plugin in Settings) to pick up changes."
 
 [linux]
 uninstall: