[Python-checkins] bpo-42918: Improve build-in function compile() in mode 'single' (GH-29934)

[ambv]

https://github.com/python/cpython/commit/28179aac796ed1debdce336c4b8ca18e8475d40d
commit: 28179aac796ed1debdce336c4b8ca18e8475d40d
branch: main
author: Weipeng Hong <hongweichen8888 at sina.com>
committer: ambv <lukasz at langa.pl>
date: 2021-12-11T00:44:26+01:00
summary:

bpo-42918: Improve build-in function compile() in mode 'single' (GH-29934)

Co-authored-by: Alex Waygood <Alex.Waygood at Gmail.com>

files:
A Misc/NEWS.d/next/Core and Builtins/2021-12-06-15-32-12.bpo-42918.Czpgtg.rst
M Lib/test/test_compile.py
M Parser/pegen.c

diff --git a/Lib/test/test_compile.py b/Lib/test/test_compile.py
index f72c7ca68f363..f4ed6c706da66 100644
--- a/Lib/test/test_compile.py
+++ b/Lib/test/test_compile.py
@@ -504,6 +504,7 @@ def test_single_statement(self):
         self.compile_single("if x:\n   f(x)")
         self.compile_single("if x:\n   f(x)\nelse:\n   g(x)")
         self.compile_single("class T:\n   pass")
+        self.compile_single("c = '''\na=1\nb=2\nc=3\n'''")
 
     def test_bad_single_statement(self):
         self.assertInvalidSingle('1\n2')
@@ -514,6 +515,7 @@ def test_bad_single_statement(self):
         self.assertInvalidSingle('f()\n# blah\nblah()')
         self.assertInvalidSingle('f()\nxy # blah\nblah()')
         self.assertInvalidSingle('x = 5 # comment\nx = 6\n')
+        self.assertInvalidSingle("c = '''\nd=1\n'''\na = 1\n\nb = 2\n")
 
     def test_particularly_evil_undecodable(self):
         # Issue 24022
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-12-06-15-32-12.bpo-42918.Czpgtg.rst b/Misc/NEWS.d/next/Core and Builtins/2021-12-06-15-32-12.bpo-42918.Czpgtg.rst
new file mode 100644
index 0000000000000..f03dadebcf3b3
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-12-06-15-32-12.bpo-42918.Czpgtg.rst	
@@ -0,0 +1,3 @@
+Fix bug where the built-in :func:`compile` function did not always raise a
+:exc:`SyntaxError` when passed multiple statements in 'single' mode. Patch by
+Weipeng Hong.
diff --git a/Parser/pegen.c b/Parser/pegen.c
index ede281ac89cd9..4158a81fd52f7 100644
--- a/Parser/pegen.c
+++ b/Parser/pegen.c
@@ -675,31 +675,13 @@ _PyPegen_number_token(Parser *p)
                            t->end_col_offset, p->arena);
 }
 
-static int // bool
-newline_in_string(Parser *p, const char *cur)
-{
-    for (const char *c = cur; c >= p->tok->buf; c--) {
-        if (*c == '\'' || *c == '"') {
-            return 1;
-        }
-    }
-    return 0;
-}
-
 /* Check that the source for a single input statement really is a single
    statement by looking at what is left in the buffer after parsing.
    Trailing whitespace and comments are OK. */
 static int // bool
 bad_single_statement(Parser *p)
 {
-    const char *cur = strchr(p->tok->buf, '\n');
-
-    /* Newlines are allowed if preceded by a line continuation character
-       or if they appear inside a string. */
-    if (!cur || (cur != p->tok->buf && *(cur - 1) == '\\')
-             || newline_in_string(p, cur)) {
-        return 0;
-    }
+    char *cur = p->tok->cur;
     char c = *cur;
 
     for (;;) {