Add SQL custom syntax test

tests/custom_syntax.rs

@@ -1,6 +1,5 @@
 #![cfg(not(feature = "no_custom_syntax"))]
-
-use rhai::{Dynamic, Engine, EvalAltResult, FnPtr, ImmutableString, LexError, ParseErrorType, Position, Scope, INT};
+use rhai::{Dynamic, Engine, EvalAltResult, ImmutableString, LexError, ParseErrorType, Position, Scope, INT};
 
 #[test]
 fn test_custom_syntax() {
@@ -432,3 +431,69 @@ fn test_custom_syntax_raw2() {
     assert_eq!(engine.eval::<INT>("#42/2").unwrap(), 21);
     assert_eq!(engine.eval::<INT>("sign(#1)").unwrap(), 1);
 }
+
+#[test]
+fn test_custom_syntax_raw_sql() {
+    let mut engine = Engine::new();
+
+    engine.register_custom_syntax_with_state_raw(
+        "SELECT",
+        |symbols, lookahead, state| {
+            // Build a SQL statement as the state
+            let mut sql: String = if state.is_unit() { Default::default() } else { state.take().cast::<ImmutableString>().into() };
+
+            // At every iteration, the last symbol is the new one
+            let r = match symbols.last().unwrap().as_str() {
+                // Terminate parsing when we see `;`
+                ";" => None,
+                // Variable substitution -- parse the following as a block
+                "$" => Some("$block$".into()),
+                // Block parsed, replace it with `?` as SQL parameter
+                "$block$" => {
+                    if !sql.is_empty() {
+                        sql.push(' ');
+                    }
+                    sql.push('?');
+                    Some(lookahead.into()) // Always accept the next token
+                }
+                // Otherwise simply concat the tokens
+                _ => {
+                    if !sql.is_empty() {
+                        sql.push(' ');
+                    }
+                    sql.push_str(symbols.last().unwrap().as_str());
+                    Some(lookahead.into()) // Always accept the next token
+                }
+            };
+
+            // SQL statement done!
+            *state = sql.into();
+
+            match lookahead {
+                // End of script?
+                "{EOF}" => Ok(None),
+                _ => Ok(r),
+            }
+        },
+        false,
+        |context, inputs, state| {
+            // Our SQL statement
+            let sql = state.as_immutable_string_ref().unwrap();
+            let mut output = sql.to_string();
+
+            // Inputs will be parameters
+            for input in inputs {
+                let value = context.eval_expression_tree(input).unwrap();
+                output.push('\n');
+                output.push_str(&value.to_string());
+            }
+
+            Ok(output.into())
+        },
+    );
+
+    let mut scope = Scope::new();
+    scope.push("id", 123 as INT);
+
+    assert_eq!(engine.eval_with_scope::<String>(&mut scope, "SELECT * FROM table WHERE id = ${id}").unwrap(), "SELECT * FROM table WHERE id = ?\n123");
+}