Fixes behaviour of example dag tests for main/other branches (#43273) (…

…#43307)

While the #43260 attempted to address the problem where example
dag importability tests should skip provider tests on non-main,
it did not actually solve the problem.

While debugging it, it turned out that since #42505, the provider
tests were not executed in main "at all" - the "providers"
directory was not included in the list of places to check for
the example dags (they were in "airflow" in v2-10-test") this is
why it "looked like" the solution worked in "main".

This PR fixes both problems:

* brings back importability of provider's example_dags in main branch
* properly excludes the providers examples in non-main branch

tests/always/test_example_dags.py

@@ -120,7 +120,14 @@ def get_python_excluded_providers_folders() -> list[str]:
 
 
 def example_not_excluded_dags(xfail_db_exception: bool = False):
-    example_dirs = ["airflow/**/example_dags/example_*.py", "tests/system/**/example_*.py"]
+    example_dirs = [
+        "airflow/**/example_dags/example_*.py",
+        "tests/system/**/example_*.py",
+        "providers/**/example_*.py",
+    ]
+
+    default_branch = os.environ.get("DEFAULT_BRANCH", "main")
+    include_providers = default_branch == "main"
 
     suspended_providers_folders = get_suspended_providers_folders()
     current_python_excluded_providers_folders = get_python_excluded_providers_folders()
@@ -135,14 +142,7 @@ def example_not_excluded_dags(xfail_db_exception: bool = False):
         for provider in current_python_excluded_providers_folders
     ]
     providers_folders = tuple([AIRFLOW_SOURCES_ROOT.joinpath(pp).as_posix() for pp in PROVIDERS_PREFIXES])
-
-    default_branch = os.environ.get("DEFAULT_BRANCH", "main")
-    include_providers = default_branch == "main"
-
     for example_dir in example_dirs:
-        if not include_providers and "providers/" in example_dir:
-            print(f"Skipping {example_dir} because providers are not included for {default_branch} branch.")
-            continue
         candidates = glob(f"{AIRFLOW_SOURCES_ROOT.as_posix()}/{example_dir}", recursive=True)
         for candidate in sorted(candidates):
             param_marks = []
@@ -167,6 +167,11 @@ def example_not_excluded_dags(xfail_db_exception: bool = False):
                 param_marks.append(pytest.mark.xfail(reason="Expected DB call", strict=True))
 
             if candidate.startswith(providers_folders):
+                if not include_providers:
+                    print(
+                        f"Skipping {candidate} because providers are not included for {default_branch} branch."
+                    )
+                    continue
                 # Do not raise an error for airflow.exceptions.RemovedInAirflow3Warning.
                 # We should not rush to enforce new syntax updates in providers
                 # because a version of Airflow that deprecates certain features may not yet be released.