strip ANSI escape codes from the output (#57)

* hook up a ansi removing function

* use a regular expression to remove ansi escapes

* prioritize CSI over C1

* check that `strip_ansi` works properly

* check that pre-formatted report strips ansi escapes

Author: keewis

parse_logs.py

@@ -12,6 +12,28 @@
 from pytest import CollectReport, TestReport
 
 test_collection_stage = "test collection session"
+fe_bytes = "[\x40-\x5f]"
+parameter_bytes = "[\x30-\x3f]"
+intermediate_bytes = "[\x20-\x2f]"
+final_bytes = "[\x40-\x7e]"
+ansi_fe_escape_re = re.compile(
+    rf"""
+    \x1B # ESC
+    (?:
+      \[  # CSI
+      {parameter_bytes}*
+      {intermediate_bytes}*
+      {final_bytes}
+      | {fe_bytes}  # single-byte Fe
+    )
+    """,
+    re.VERBOSE,
+)
+
+
+def strip_ansi(msg):
+    """strip all ansi escape sequences"""
+    return ansi_fe_escape_re.sub("", msg)
 
 
 @dataclass
@@ -45,6 +67,9 @@ class PreformattedReport:
     variant: str | None
     message: str
 
+    def __post_init__(self):
+        self.message = strip_ansi(self.message)
+
 
 @dataclass
 class CollectionError:

test_parse_log.py

@@ -19,6 +19,30 @@
 messages = st.text()
 
 
+def ansi_csi_escapes():
+    parameter_bytes = st.lists(st.characters(min_codepoint=0x30, max_codepoint=0x3F))
+    intermediate_bytes = st.lists(st.characters(min_codepoint=0x20, max_codepoint=0x2F))
+    final_bytes = st.characters(min_codepoint=0x40, max_codepoint=0x7E)
+
+    return st.builds(
+        lambda *args: "".join(["\x1b[", *args]),
+        parameter_bytes.map("".join),
+        intermediate_bytes.map("".join),
+        final_bytes,
+    )
+
+
+def ansi_c1_escapes():
+    byte_ = st.characters(
+        codec="ascii", min_codepoint=0x40, max_codepoint=0x5F, exclude_characters=["["]
+    )
+    return st.builds(lambda b: f"\x1b{b}", byte_)
+
+
+def ansi_fe_escapes():
+    return ansi_csi_escapes() | ansi_c1_escapes()
+
+
 def preformatted_reports():
     return st.tuples(filepaths, names, variants | st.none(), messages).map(
         lambda x: parse_logs.PreformattedReport(*x)
@@ -47,3 +71,23 @@ def test_truncate(reports, max_chars):
     formatted = parse_logs.truncate(reports, max_chars=max_chars, py_version=py_version)
 
     assert formatted is None or len(formatted) <= max_chars
+
+
+@given(st.lists(ansi_fe_escapes()).map("".join))
+def test_strip_ansi_multiple(escapes):
+    assert parse_logs.strip_ansi(escapes) == ""
+
+
+@given(ansi_fe_escapes())
+def test_strip_ansi(escape):
+    message = f"some {escape}text"
+
+    assert parse_logs.strip_ansi(message) == "some text"
+
+
+@given(ansi_fe_escapes())
+def test_preformatted_report_ansi(escape):
+    actual = parse_logs.PreformattedReport(
+        filepath="a", name="b", variant=None, message=f"{escape}text"
+    )
+    assert actual.message == "text"