Escape the quote in a filename even if text starts with a quote

docs/source/whatsnew/pr/escape-quoted-filenames.rst

@@ -0,0 +1,2 b''
+- Quotes in a filename are always escaped during tab-completion on non-Windows.
+  :ghpull:`10069`

IPython/core/completer.py

@@ -226,13 +226,13 b' def has_open_quotes(s):'
         return False
 
 
-def protect_filename(s):
+def protect_filename(s, protectables=PROTECTABLES):
     """Escape a string to protect certain characters."""
-    if set(s) & set(PROTECTABLES):
+    if set(s) & set(protectables):
         if sys.platform == "win32":
             return '"' + s + '"'
         else:
-            return "".join(("\\" + c if c in PROTECTABLES else c) for c in s)
+            return "".join(("\\" + c if c in protectables else c) for c in s)
     else:
         return s
 
@@ -1133,9 +1133,10 b' class IPCompleter(Completer):'
         else:
             if open_quotes:
                 # if we have a string with an open quote, we don't need to
-                # protect the names at all (and we _shouldn't_, as it
-                # would cause bugs when the filesystem call is made).
-                matches = m0
+                # protect the names beyond the quote (and we _shouldn't_, as
+                # it would cause bugs when the filesystem call is made).
+                matches = m0 if sys.platform == "win32" else\
+                    [protect_filename(f, open_quotes) for f in m0]
             else:
                 matches = [text_prefix +
                            protect_filename(f) for f in m0]

IPython/core/tests/test_completer.py

@@ -274,6 +274,37 b' def test_local_file_completions():'
         nt.assert_true(comp.issubset(set(c)))
 
 
+def test_quoted_file_completions():
+    ip = get_ipython()
+    with TemporaryWorkingDirectory():
+        name = "foo'bar"
+        open(name, 'w').close()
+
+        # Don't escape Windows
+        escaped = name if sys.platform == "win32" else "foo\\'bar"
+
+        # Single quote matches embedded single quote
+        text = "open('foo"
+        c = ip.Completer._complete(cursor_line=0,
+                                   cursor_pos=len(text),
+                                   full_text=text)[1]
+        nt.assert_equal(c, [escaped])
+
+        # Double quote requires no escape
+        text = 'open("foo'
+        c = ip.Completer._complete(cursor_line=0,
+                                   cursor_pos=len(text),
+                                   full_text=text)[1]
+        nt.assert_equal(c, [name])
+
+        # No quote requires an escape
+        text = '%ls foo'
+        c = ip.Completer._complete(cursor_line=0,
+                                   cursor_pos=len(text),
+                                   full_text=text)[1]
+        nt.assert_equal(c, [escaped])
+
+
 def test_jedi():
     """
     A couple of issue we had with Jedi