gh-112343: pdb: Use tokenize to replace convenience variables (#112380)

Lib/pdb.py

@@ -76,6 +76,7 @@ import bdb
 import dis
 import code
 import glob
+import token
 import codeop
 import pprint
 import signal
@@ -601,6 +602,39 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         except:
             self._error_exc()
 
+    def _replace_convenience_variables(self, line):
+        """Replace the convenience variables in 'line' with their values.
+           e.g. $foo is replaced by __pdb_convenience_variables["foo"].
+           Note: such pattern in string literals will be skipped"""
+
+        if "$" not in line:
+            return line
+
+        dollar_start = dollar_end = -1
+        replace_variables = []
+        try:
+            for t in tokenize.generate_tokens(io.StringIO(line).readline):
+                token_type, token_string, start, end, _ = t
+                if token_type == token.OP and token_string == '$':
+                    dollar_start, dollar_end = start, end
+                elif start == dollar_end and token_type == token.NAME:
+                    # line is a one-line command so we only care about column
+                    replace_variables.append((dollar_start[1], end[1], token_string))
+        except tokenize.TokenError:
+            return line
+
+        if not replace_variables:
+            return line
+
+        last_end = 0
+        line_pieces = []
+        for start, end, name in replace_variables:
+            line_pieces.append(line[last_end:start] + f'__pdb_convenience_variables["{name}"]')
+            last_end = end
+        line_pieces.append(line[last_end:])
+
+        return ''.join(line_pieces)
+
     def precmd(self, line):
         """Handle alias expansion and ';;' separator."""
         if not line.strip():
@@ -635,7 +669,7 @@ class Pdb(bdb.Bdb, cmd.Cmd):
                 line = line[:marker].rstrip()
 
         # Replace all the convenience variables
-        line = re.sub(r'\$([a-zA-Z_][a-zA-Z0-9_]*)', r'__pdb_convenience_variables["\1"]', line)
+        line = self._replace_convenience_variables(line)
 
         return line
 

Lib/test/test_pdb.py

@@ -847,9 +847,12 @@ def test_convenience_variables():
 
     >>> with PdbTestInput([  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
     ...     '$_frame.f_lineno', # Check frame convenience variable
+    ...     '$ _frame',         # This should be a syntax error
     ...     '$a = 10',          # Set a convenience variable
     ...     '$a',               # Print its value
+    ...     'p "$a"',           # Print the string $a
     ...     'p $a + 2',         # Do some calculation
+    ...     'p f"$a = {$a}"',   # Make sure $ in string is not converted and f-string works
     ...     'u',                # Switch frame
     ...     '$_frame.f_lineno', # Make sure the frame changed
     ...     '$a',               # Make sure the value persists
@@ -869,11 +872,17 @@ def test_convenience_variables():
     -> try:
     (Pdb) $_frame.f_lineno
     3
+    (Pdb) $ _frame
+    *** SyntaxError: invalid syntax
     (Pdb) $a = 10
     (Pdb) $a
     10
+    (Pdb) p "$a"
+    '$a'
     (Pdb) p $a + 2
     12
+    (Pdb) p f"$a = {$a}"
+    '$a = 10'
     (Pdb) u
     > <doctest test.test_pdb.test_convenience_variables[1]>(2)test_function()
     -> util_function()

Misc/NEWS.d/next/Library/2023-11-24-19-08-50.gh-issue-112343.RarGFC.rst

@@ -0,0 +1 @@
+Improve handling of pdb convenience variables to avoid replacing string contents.