Merge 'Fix handling of empty strings in prepared statements' from Diego Reis

When `prepare()` is called with an empty string it should throw an error
(e.g `ApiMisuse` in rusqlite). I'm testing only in JS but it should
throw to any bind.

Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>

Closes #1473

bindings/javascript/__test__/better-sqlite3.spec.mjs

@@ -31,6 +31,13 @@ test("Statement.run() returns correct result object", async (t) => {
   t.deepEqual(rows, { changes: 1, lastInsertRowid: 1 });
 });
 
+test("Empty prepared statement should throw", async (t) => {
+    const [db] = await connect(":memory:");
+    t.throws(() => {
+        db.prepare("");
+    }, { instanceOf: Error });
+});
+
 const connect = async (path) => {
   const db = new Database(path);
   return [db];

bindings/javascript/__test__/limbo.spec.mjs

@@ -1,27 +1,26 @@
 import test from "ava";
 
-import { Database } from "../index.js"; 
+import { Database } from "../index.js";
 
 test("Open in-memory database", async (t) => {
-    const [db] = await connect(":memory:");
-    t.is(db.memory, true);
+  const [db] = await connect(":memory:");
+  t.is(db.memory, true);
 });
 
-
 test("Statement.get() returns data", async (t) => {
-    const [db] = await connect(":memory:");
-    const stmt = db.prepare("SELECT 1");
-    const result = stmt.get();
-    t.is(result["1"], 1);
-    const result2 = stmt.get();
-    t.is(result2["1"], 1);
+  const [db] = await connect(":memory:");
+  const stmt = db.prepare("SELECT 1");
+  const result = stmt.get();
+  t.is(result["1"], 1);
+  const result2 = stmt.get();
+  t.is(result2["1"], 1);
 });
 
 test("Statement.get() returns null when no data", async (t) => {
-    const [db] = await connect(":memory:");
-    const stmt = db.prepare("SELECT 1 WHERE 1 = 2");
-    const result = stmt.get();
-    t.is(result, undefined);
+  const [db] = await connect(":memory:");
+  const stmt = db.prepare("SELECT 1 WHERE 1 = 2");
+  const result = stmt.get();
+  t.is(result, undefined);
 });
 
 // run() isn't 100% compatible with better-sqlite3
@@ -30,11 +29,21 @@ test("Statement.run() returns correct result object", async (t) => {
   const [db] = await connect(":memory:");
   db.prepare("CREATE TABLE users (name TEXT)").run();
   db.prepare("INSERT INTO users (name) VALUES (?)").run(["Alice"]);
-  let rows = db.prepare("SELECT * FROM users").all()
+  let rows = db.prepare("SELECT * FROM users").all();
   t.deepEqual(rows, [{ name: "Alice" }]);
 });
 
+test("Empty prepared statement should throw", async (t) => {
+  const [db] = await connect(":memory:");
+  t.throws(
+    () => {
+      db.prepare("");
+    },
+    { instanceOf: Error },
+  );
+});
+
 const connect = async (path) => {
-    const db = new Database(path);
-    return [db];
+  const db = new Database(path);
+  return [db];
 };

core/lib.rs

@@ -325,37 +325,40 @@ pub struct Connection {
 
 impl Connection {
     pub fn prepare(self: &Rc<Connection>, sql: impl AsRef<str>) -> Result<Statement> {
+        if sql.as_ref().is_empty() {
+            return Err(LimboError::InvalidArgument(
+                "The supplied SQL string contains no statements".to_string(),
+            ));
+        }
+
         let sql = sql.as_ref();
         tracing::trace!("Preparing: {}", sql);
         let mut parser = Parser::new(sql.as_bytes());
         let cmd = parser.next()?;
         let syms = self.syms.borrow();
-        if let Some(cmd) = cmd {
-            match cmd {
-                Cmd::Stmt(stmt) => {
-                    let program = Rc::new(translate::translate(
-                        self.schema
-                            .try_read()
-                            .ok_or(LimboError::SchemaLocked)?
-                            .deref(),
-                        stmt,
-                        self.header.clone(),
-                        self.pager.clone(),
-                        Rc::downgrade(self),
-                        &syms,
-                        QueryMode::Normal,
-                    )?);
-                    Ok(Statement::new(
-                        program,
-                        self._db.mv_store.clone(),
-                        self.pager.clone(),
-                    ))
-                }
-                Cmd::Explain(_stmt) => todo!(),
-                Cmd::ExplainQueryPlan(_stmt) => todo!(),
+        let cmd = cmd.expect("Successful parse on nonempty input string should produce a command");
+        match cmd {
+            Cmd::Stmt(stmt) => {
+                let program = Rc::new(translate::translate(
+                    self.schema
+                        .try_read()
+                        .ok_or(LimboError::SchemaLocked)?
+                        .deref(),
+                    stmt,
+                    self.header.clone(),
+                    self.pager.clone(),
+                    Rc::downgrade(self),
+                    &syms,
+                    QueryMode::Normal,
+                )?);
+                Ok(Statement::new(
+                    program,
+                    self._db.mv_store.clone(),
+                    self.pager.clone(),
+                ))
             }
-        } else {
-            todo!()
+            Cmd::Explain(_stmt) => todo!(),
+            Cmd::ExplainQueryPlan(_stmt) => todo!(),
         }
     }