use setter for stats, handling main color

src/_pytest/terminal.py

@@ -248,6 +248,8 @@ def __init__(self, config: Config, file=None) -> None:
         self._showfspath = None
 
         self.stats = {}  # type: Dict[str, List[Any]]
+        self._main_color = None  # type: Optional[str]
+        self._known_types = None  # type: Optional[List]
         self.startdir = config.invocation_dir
         if file is None:
             file = sys.stdout
@@ -366,6 +368,13 @@ def section(self, title, sep="=", **kw):
     def line(self, msg, **kw):
         self._tw.line(msg, **kw)
 
+    def _add_stats(self, category: str, items: List) -> None:
+        if category not in self.stats:
+            self.stats[category] = items
+            self._set_main_color()
+        else:
+            self.stats[category].extend(items)
+
     def pytest_internalerror(self, excrepr):
         for line in str(excrepr).split("\n"):
             self.write_line("INTERNALERROR> " + line)
@@ -375,15 +384,14 @@ def pytest_warning_captured(self, warning_message, item):
         # from _pytest.nodes import get_fslocation_from_item
         from _pytest.warnings import warning_record_to_str
 
-        warnings = self.stats.setdefault("warnings", [])
         fslocation = warning_message.filename, warning_message.lineno
         message = warning_record_to_str(warning_message)
 
         nodeid = item.nodeid if item is not None else ""
         warning_report = WarningReport(
             fslocation=fslocation, message=message, nodeid=nodeid
         )
-        warnings.append(warning_report)
+        self._add_stats("warnings", [warning_report])
 
     def pytest_plugin_registered(self, plugin):
         if self.config.option.traceconfig:
@@ -394,7 +402,7 @@ def pytest_plugin_registered(self, plugin):
             self.write_line(msg)
 
     def pytest_deselected(self, items):
-        self.stats.setdefault("deselected", []).extend(items)
+        self._add_stats("deselected", items)
 
     def pytest_runtest_logstart(self, nodeid, location):
         # ensure that the path is printed before the
@@ -415,7 +423,7 @@ def pytest_runtest_logreport(self, report: TestReport) -> None:
             word, markup = word
         else:
             markup = None
-        self.stats.setdefault(category, []).append(rep)
+        self._add_stats(category, [rep])
         if not letter and not word:
             # probably passed setup/teardown
             return
@@ -529,9 +537,9 @@ def pytest_collection(self):
 
     def pytest_collectreport(self, report: CollectReport) -> None:
         if report.failed:
-            self.stats.setdefault("error", []).append(report)
+            self._add_stats("error", [report])
         elif report.skipped:
-            self.stats.setdefault("skipped", []).append(report)
+            self._add_stats("skipped", [report])
         items = [x for x in report.result if isinstance(x, pytest.Item)]
         self._numcollected += len(items)
         if self.isatty:
@@ -1011,6 +1019,11 @@ def show_skipped(lines: List[str]) -> None:
                 self.write_line(line)
 
     def _get_main_color(self) -> Tuple[str, List[str]]:
+        if self._main_color is None or self._known_types is None:
+            self._main_color, self._known_types = self._set_main_color()
+        return self._main_color, self._known_types
+
+    def _set_main_color(self) -> Tuple[str, List[str]]:
         stats = self.stats
         known_types = (
             "failed passed skipped deselected xfailed xpassed warnings error".split()
@@ -1031,10 +1044,9 @@ def _get_main_color(self) -> Tuple[str, List[str]]:
             main_color = "green"
         else:
             main_color = "yellow"
-
         return main_color, known_types
 
-    def build_summary_stats_line(self):
+    def build_summary_stats_line(self) -> Tuple[List[Tuple[str, Dict[str, bool]]], str]:
         main_color, known_types = self._get_main_color()
 
         parts = []

testing/test_terminal.py

@@ -1441,6 +1441,9 @@ def test_summary_stats(tr, exp_line, exp_color, stats_arg):
     tr._testscollected = 0
     assert tr._is_last_item
 
+    # Reset cache.
+    tr._main_color = None
+
     print("Based on stats: %s" % stats_arg)
     print('Expect summary: "{}"; with color "{}"'.format(exp_line, exp_color))
     (line, color) = tr.build_summary_stats_line()