Respect --fulltrace with collection errors

changelog/6247.improvement.rst

@@ -0,0 +1 @@
+``--fulltrace`` is honored with collection errors.

src/_pytest/nodes.py

@@ -365,12 +365,14 @@ def collect(self):
 
     def repr_failure(self, excinfo):
         """ represent a collection failure. """
-        if excinfo.errisinstance(self.CollectError):
+        if excinfo.errisinstance(self.CollectError) and not self.config.getoption(
+            "fulltrace", False
+        ):
             exc = excinfo.value
             return str(exc.args[0])
 
         # Respect explicit tbstyle option, but default to "short"
-        # (None._repr_failure_py defaults to "long" without "fulltrace" option).
+        # (_repr_failure_py uses "long" with "fulltrace" option always).
         tbstyle = self.config.getoption("tbstyle", "auto")
         if tbstyle == "auto":
             tbstyle = "short"

testing/python/collect.py

@@ -1210,6 +1210,28 @@ def test_syntax_error_with_non_ascii_chars(testdir):
     result.stdout.fnmatch_lines(["*ERROR collecting*", "*SyntaxError*", "*1 error in*"])
 
 
+def test_collecterror_with_fulltrace(testdir):
+    testdir.makepyfile("assert 0")
+    result = testdir.runpytest("--fulltrace")
+    result.stdout.fnmatch_lines(
+        [
+            "collected 0 items / 1 error",
+            "",
+            "*= ERRORS =*",
+            "*_ ERROR collecting test_collecterror_with_fulltrace.py _*",
+            "",
+            "*/_pytest/python.py:*: ",
+            "_ _ _ _ _ _ _ _ *",
+            "",
+            ">   assert 0",
+            "E   assert 0",
+            "",
+            "test_collecterror_with_fulltrace.py:1: AssertionError",
+            "*! Interrupted: 1 error during collection !*",
+        ]
+    )
+
+
 def test_skip_duplicates_by_default(testdir):
     """Test for issue https://github.com/pytest-dev/pytest/issues/1609 (#1609)