Add tests for cyclic variables check

dev-requirements.txt

@@ -8,3 +8,4 @@ pytest-env
 pytest-pep8
 pytest-pylint
 pytest-xdist
+pytest-timeout

tests/format/variables.py

 import os
 import pytest
+import sys
 from buildstream import _yaml
 from buildstream._exceptions import ErrorDomain, LoadErrorReason
 from tests.testutils.runcli import cli
@@ -72,3 +73,20 @@ def test_missing_variable(cli, datafiles, tmpdir):
     ])
     result.assert_main_error(ErrorDomain.LOAD,
                              LoadErrorReason.UNRESOLVED_VARIABLE)
+
+@pytest.mark.timeout(3, method="signal")
+@pytest.mark.datafiles(os.path.join(DATA_DIR, 'cyclic_variables'))
+def test_cyclic_variables(cli, datafiles):
+    print_warning("Performing cyclic test, if this test times out it will " +
+                  "exit the test sequence")
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    result = cli.run(project=project, silent=True, args=[
+        "build", "cyclic.bst"
+    ])
+    result.assert_main_error(ErrorDomain.LOAD, LoadErrorReason.RECURSIVE_VARIABLE)
+
+
+def print_warning(msg):
+    RED, END = "\033[91m", "\033[0m"
+    print(("\n{}{}{}").format(RED, msg, END), file=sys.stderr)
+

tests/format/variables/cyclic_variables/cyclic.bst

+kind: manual
+
+variables:
+  a: "%{prefix}/a"
+  prefix: "%{a}/some_prefix/"
\ No newline at end of file

tests/format/variables/cyclic_variables/project.conf

+name: test

tests/testutils/runcli.py

@@ -94,14 +94,28 @@ class Result():
     #    error_reason (any): The reason field of the error which occurred
     #    fail_message (str): An optional message to override the automatic
     #                        assertion error messages
+    #    debug (bool): If true, prints information regarding the exit state of the result()
     # Raises:
     #    (AssertionError): If any of the assertions fail
     #
     def assert_main_error(self,
                           error_domain,
                           error_reason,
-                          fail_message=''):
-
+                          fail_message='',
+                          *, debug=False):
+        if debug:
+            print(
+                """
+                Exit code: {}
+                Exception: {}
+                Domain:    {}
+                Reason:    {}
+                """.format(
+                    self.exit_code,
+                    self.exception,
+                    self.exception.domain,
+                    self.exception.reason
+                ))
         assert self.exit_code == -1, fail_message
         assert self.exc is not None, fail_message
         assert self.exception is not None, fail_message