gh-120767: Add REPL history navigation with partial text

Lib/_pyrepl/reader.py

@@ -143,8 +143,8 @@ def make_default_commands() -> dict[CommandName, type[Command]]:
     + [(c, "self-insert") for c in map(chr, range(32, 127)) if c != "\\"]
     + [(c, "self-insert") for c in map(chr, range(128, 256)) if c.isalpha()]
     + [
-        (r"\<up>", "up"),
-        (r"\<down>", "down"),
+        (r"\<up>", "history-search-backward"),
+        (r"\<down>", "history-search-forward"),
         (r"\<left>", "left"),
         (r"\C-\<left>", "backward-word"),
         (r"\<right>", "right"),

Lib/test/test_pyrepl/test_pyrepl.py

@@ -689,6 +689,46 @@ def test_history_navigation_with_up_arrow(self):
         self.assertEqual(output, "1+1")
         self.assertEqual(clean_screen(reader.screen), "1+1")
 
+    def test_history_navigation_with_up_arrow_and_partial_text(self):
+        events = itertools.chain(
+            code_to_events("spam = 1\nham = 2\neggs = 3\nsp"),
+            [
+                Event(evt="key", data="up", raw=bytearray(b"\x1bOA")),
+                Event(evt="key", data="\n", raw=bytearray(b"\n")),
+            ],
+        )
+
+        reader = self.prepare_reader(events)
+
+        output = multiline_input(reader)
+        self.assertEqual(output, "spam = 1")
+
+    def test_history_navigation_with_up_arrow_and_partial_text_with_similar_entries(self):
+        events = itertools.chain(
+            code_to_events("a=111\na=11\na=1\na="),
+            [
+                Event(evt="key", data="up", raw=bytearray(b"\x1bOA")),
+                Event(evt="key", data="up", raw=bytearray(b"\x1bOA")),
+                Event(evt="key", data="up", raw=bytearray(b"\x1bOA")),
+                Event(evt="key", data="\n", raw=bytearray(b"\n")),
+            ],
+        )
+
+        reader = self.prepare_reader(events)
+        print()
+        output = multiline_input(reader)
+        self.assertEqual(output, "a=111")
+        self.assertEqual(clean_screen(reader.screen), "a=111")
+        output = multiline_input(reader)
+        self.assertEqual(output, "a=11")
+        self.assertEqual(clean_screen(reader.screen), "a=11")
+        output = multiline_input(reader)
+        self.assertEqual(output, "a=1")
+        self.assertEqual(clean_screen(reader.screen), "a=1")
+        output = multiline_input(reader)
+        self.assertEqual(output, "a=111")
+        self.assertEqual(clean_screen(reader.screen), "a=111")
+
     def test_history_with_multiline_entries(self):
         code = "def foo():\nx = 1\ny = 2\nz = 3\n\ndef bar():\nreturn 42\n\n"
         events = list(itertools.chain(

Misc/NEWS.d/next/Library/2024-07-17-12-13-30.gh-issue-120767.BKyogz.rst

@@ -0,0 +1,4 @@
+Enhance REPL history navigation with partial text support
+
+The REPL now correctly navigates history based on partial text
+in the buffer when using the up arrow.