fix: complete readline prompt coverage

tests/test_readline_prompts.py

@@ -0,0 +1,84 @@
+import ast
+import re
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+SOURCE_FILES = tuple(sorted([
+    *ROOT.glob("s*/code.py"),
+    *ROOT.glob("agents/*.py"),
+]))
+ANSI_ESCAPE = re.compile(r"\x1b\[[0-9;]*m")
+
+
+def string_assignments(tree: ast.AST) -> dict[str, str]:
+    values = {}
+    for node in ast.walk(tree):
+        if not isinstance(node, (ast.Assign, ast.AnnAssign)):
+            continue
+        targets = node.targets if isinstance(node, ast.Assign) else [node.target]
+        value = node.value
+        if not isinstance(value, ast.Constant) or not isinstance(value.value, str):
+            continue
+        for target in targets:
+            if isinstance(target, ast.Name):
+                values[target.id] = value.value
+    return values
+
+
+def input_prompts(path: Path) -> list[tuple[int, str]]:
+    tree = ast.parse(path.read_text(encoding="utf-8"))
+    assignments = string_assignments(tree)
+    prompts = []
+    for node in ast.walk(tree):
+        if not isinstance(node, ast.Call):
+            continue
+        is_input = isinstance(node.func, ast.Name) and node.func.id == "input"
+        is_console_ask = isinstance(node.func, ast.Attribute) and node.func.attr == "ask"
+        if not (is_input or is_console_ask):
+            continue
+        if not node.args:
+            if is_console_ask and "READLINE_PROMPT" in assignments:
+                prompts.append((node.lineno, assignments["READLINE_PROMPT"]))
+            continue
+        argument = node.args[0]
+        if isinstance(argument, ast.Constant) and isinstance(argument.value, str):
+            prompts.append((node.lineno, argument.value))
+        elif isinstance(argument, ast.Name) and argument.id in assignments:
+            prompts.append((node.lineno, assignments[argument.id]))
+    return prompts
+
+
+def test_colored_input_prompts_mark_ansi_as_zero_width() -> None:
+    checked = 0
+    invalid = []
+    for path in SOURCE_FILES:
+        for lineno, prompt in input_prompts(path):
+            escapes = list(ANSI_ESCAPE.finditer(prompt))
+            if not escapes:
+                assert "\x01" not in prompt and "\x02" not in prompt
+                continue
+            checked += 1
+            for escape in escapes:
+                marked = (
+                    prompt[escape.start() - 1:escape.start()] == "\x01"
+                    and prompt[escape.end():escape.end() + 1] == "\x02"
+                )
+                if not marked:
+                    invalid.append(f"{path.relative_to(ROOT)}:{lineno}")
+                    break
+
+    assert checked, "expected at least one colored input prompt"
+    assert not invalid, "ANSI escapes missing Readline markers:\n" + "\n".join(invalid)
+
+
+def test_async_redraw_prompts_keep_markers_out_of_display_text() -> None:
+    for lesson in ("s15_integrated_harness", "s16_workflow_runtime"):
+        path = ROOT / lesson / "code.py"
+        tree = ast.parse(path.read_text(encoding="utf-8"))
+        assignments = string_assignments(tree)
+        display_prompt = assignments["PROMPT"]
+        readline_prompt = assignments["READLINE_PROMPT"]
+
+        assert "\x01" not in display_prompt and "\x02" not in display_prompt
+        assert readline_prompt.replace("\x01", "").replace("\x02", "") == display_prompt