From 0f500deca6b59826ef89064e9bd6f1893737ba57 Mon Sep 17 00:00:00 2001
From: Bruno Oliveira <nicoddemus@gmail.com>
Date: Sat, 30 Nov 2019 12:11:29 -0300
Subject: [PATCH] Ensure cache supporting files still exist after --cache-clear

Fix #6290
---
 changelog/6290.bugfix.rst     |  1 +
 src/_pytest/cacheprovider.py  | 27 ++++++++++++++++++++-------
 testing/test_cacheprovider.py |  1 +
 3 files changed, 22 insertions(+), 7 deletions(-)
 create mode 100644 changelog/6290.bugfix.rst

diff --git a/changelog/6290.bugfix.rst b/changelog/6290.bugfix.rst
new file mode 100644
index 00000000000..f6f1560d493
--- /dev/null
+++ b/changelog/6290.bugfix.rst
@@ -0,0 +1 @@
+The supporting files in the ``.pytest_cache`` directory are kept with ``--cache-clear``, which only clears cached values now.
diff --git a/src/_pytest/cacheprovider.py b/src/_pytest/cacheprovider.py
index 6e53545d630..802c5212267 100755
--- a/src/_pytest/cacheprovider.py
+++ b/src/_pytest/cacheprovider.py
@@ -44,14 +44,27 @@ class Cache:
     _cachedir = attr.ib(repr=False)
     _config = attr.ib(repr=False)
 
+    # sub-directory under cache-dir for directories created by "makedir"
+    _CACHE_PREFIX_DIRS = "d"
+
+    # sub-directory under cache-dir for values created by "set"
+    _CACHE_PREFIX_VALUES = "v"
+
     @classmethod
     def for_config(cls, config):
         cachedir = cls.cache_dir_from_config(config)
-        if config.getoption("cacheclear") and cachedir.exists():
-            rm_rf(cachedir)
-            cachedir.mkdir()
+        if config.getoption("cacheclear") and cachedir.is_dir():
+            cls.clear_cache(cachedir)
         return cls(cachedir, config)
 
+    @classmethod
+    def clear_cache(cls, cachedir: Path):
+        """Clears the sub-directories used to hold cached directories and values."""
+        for prefix in (cls._CACHE_PREFIX_DIRS, cls._CACHE_PREFIX_VALUES):
+            d = cachedir / prefix
+            if d.is_dir():
+                rm_rf(d)
+
     @staticmethod
     def cache_dir_from_config(config):
         return resolve_from_str(config.getini("cache_dir"), config.rootdir)
@@ -79,12 +92,12 @@ def makedir(self, name):
         name = Path(name)
         if len(name.parts) > 1:
             raise ValueError("name is not allowed to contain path separators")
-        res = self._cachedir.joinpath("d", name)
+        res = self._cachedir.joinpath(self._CACHE_PREFIX_DIRS, name)
         res.mkdir(exist_ok=True, parents=True)
         return py.path.local(res)
 
     def _getvaluepath(self, key):
-        return self._cachedir.joinpath("v", Path(key))
+        return self._cachedir.joinpath(self._CACHE_PREFIX_VALUES, Path(key))
 
     def get(self, key, default):
         """ return cached value for the given key.  If no value
@@ -417,7 +430,7 @@ def cacheshow(config, session):
 
     dummy = object()
     basedir = config.cache._cachedir
-    vdir = basedir / "v"
+    vdir = basedir / Cache._CACHE_PREFIX_VALUES
     tw.sep("-", "cache values for %r" % glob)
     for valpath in sorted(x for x in vdir.rglob(glob) if x.is_file()):
         key = valpath.relative_to(vdir)
@@ -429,7 +442,7 @@ def cacheshow(config, session):
             for line in pformat(val).splitlines():
                 tw.line("  " + line)
 
-    ddir = basedir / "d"
+    ddir = basedir / Cache._CACHE_PREFIX_DIRS
     if ddir.is_dir():
         contents = sorted(ddir.rglob(glob))
         tw.sep("-", "cache directories for %r" % glob)
diff --git a/testing/test_cacheprovider.py b/testing/test_cacheprovider.py
index 0e1194b02a0..f0b279abf31 100644
--- a/testing/test_cacheprovider.py
+++ b/testing/test_cacheprovider.py
@@ -270,6 +270,7 @@ def test_3(): assert 0
         )
         result = testdir.runpytest(str(p), "--lf", "--cache-clear")
         result.stdout.fnmatch_lines(["*1 failed*2 passed*"])
+        assert testdir.tmpdir.join(".pytest_cache", "README.md").isfile()
 
         # Run this again to make sure clear-cache is robust
         if os.path.isdir(".pytest_cache"):