add const string multiply test

Author: xuantengh

Lib/test/test_compile.py

@@ -906,6 +906,9 @@ def with_fstring():
 
             def with_const_expression():
                 "also" + " not docstring"
+
+            def multiple_const_strings():
+                "not docstring " * 3
             """)
 
         for opt in [0, 1, 2]:
@@ -922,6 +925,7 @@ def with_const_expression():
                     self.assertIsNone(ns['two_strings'].__doc__)
                 self.assertIsNone(ns['with_fstring'].__doc__)
                 self.assertIsNone(ns['with_const_expression'].__doc__)
+                self.assertIsNone(ns['multiple_const_strings'].__doc__)
 
     @support.cpython_only
     def test_docstring_interactive_mode(self):

Python/ast_opt.c

@@ -676,7 +676,23 @@ static int astfold_type_param(type_param_ty node_, PyArena *ctx_, _PyASTOptimize
 static int
 astfold_body(asdl_stmt_seq *stmts, PyArena *ctx_, _PyASTOptimizeState *state)
 {
+    int docstring = _PyAST_GetDocString(stmts) != NULL;
     CALL_SEQ(astfold_stmt, stmt, stmts);
+    if (!docstring && _PyAST_GetDocString(stmts) != NULL) {
+        stmt_ty st = (stmt_ty)asdl_seq_GET(stmts, 0);
+        asdl_expr_seq *values = _Py_asdl_expr_seq_new(1, ctx_);
+        if (!values) {
+            return 0;
+        }
+        asdl_seq_SET(values, 0, st->v.Expr.value);
+        expr_ty expr = _PyAST_JoinedStr(values, st->lineno, st->col_offset,
+                                        st->end_lineno, st->end_col_offset,
+                                        ctx_);
+        if (!expr) {
+            return 0;
+        }
+        st->v.Expr.value = expr;
+    }
     return 1;
 }