Fail gracefully if no templates match wildcard

*Description of changes:*

`cfn-lint` currently fails if there are no Cloudformation templates that
match the pattern specified either via CLI arguments or via config file.

```
$ cfn-lint "cfn/**/*.y*ml"
2024-08-16 13:41:38,381 - cfnlint.decode.decode - ERROR - Template file not found: cfn/**/*.y*ml
E0000 Template file not found: cfn/**/*.y*ml
cfn/**/*.y*ml:1:1

$ echo $?
2
```

It appears that when the glob pattern matching does not find any match,
the actual string is appended as a template file.

This PR improves the handling of wildcard templates by ensuring only
matched templates are added to be linted by `cfn-lint` and would
gracefully exit without an output message.

If run with debug switch, it lists the Cloudformation templates found by the glob.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

src/cfnlint/config.py

@@ -624,6 +624,7 @@ class ConfigMixIn(TemplateArgs, CliArgs, ConfigFileArgs):
 
     def __init__(self, cli_args: list[str] | None = None, **kwargs: Unpack[ManualArgs]):
         self._manual_args = kwargs or ManualArgs()
+        self._templates_to_process = False
         CliArgs.__init__(self, cli_args)
         # configure debug as soon as we can
         TemplateArgs.__init__(self, {})
@@ -732,23 +733,47 @@ def format(self):
 
     @property
     def templates(self):
-        templates_args = self._get_argument_value("templates", False, True)
-        template_alt_args = self._get_argument_value("template_alt", False, False)
-        if template_alt_args:
-            filenames = template_alt_args
-        elif templates_args:
-            filenames = templates_args
+        """
+
+        Returns a list of Cloudformation templates to lint.
+
+        Order of precedence:
+        - Filenames provided via `-t` CLI
+        - Filenames specified in the config file.
+        - Arguments provided via `cfn-lint` CLI.
+        """
+
+        all_filenames = []
+
+        cli_alt_args = self._get_argument_value("template_alt", False, False)
+        file_args = self._get_argument_value("templates", False, True)
+        cli_args = self._get_argument_value("templates", False, False)
+
+        if cli_alt_args:
+            filenames = cli_alt_args
+        elif file_args:
+            filenames = file_args
+        elif cli_args:
+            filenames = cli_args
         else:
+            # No filenames found, could be piped in or be using the api.
             return None
 
-        # if only one is specified convert it to array
+        # If we're still haven't returned, we've got templates to lint.
+        # Build up list of templates to lint.
+        self.templates_to_process = True
+
         if isinstance(filenames, str):
             filenames = [filenames]
 
         ignore_templates = self._ignore_templates()
-        all_filenames = self._glob_filenames(filenames)
+        all_filenames.extend(self._glob_filenames(filenames))
 
-        return [i for i in all_filenames if i not in ignore_templates]
+        found_files = [i for i in all_filenames if i not in ignore_templates]
+        LOGGER.debug(
+            f"List of Cloudformation Templates to lint: {found_files} from {filenames}"
+        )
+        return found_files
 
     def _ignore_templates(self):
         ignore_template_args = self._get_argument_value("ignore_templates", False, True)
@@ -770,12 +795,11 @@ def _glob_filenames(self, filenames: Sequence[str]) -> list[str]:
 
         for filename in filenames:
             add_filenames = glob.glob(filename, recursive=True)
-            # only way to know of the glob failed is to test it
-            # then add the filename as requested
-            if not add_filenames:
-                all_filenames.append(filename)
-            else:
+
+            if isinstance(add_filenames, list):
                 all_filenames.extend(add_filenames)
+            else:
+                LOGGER.error(f"{filename} could not be processed by glob.glob")
 
         return sorted(list(map(str, map(Path, all_filenames))))
 
@@ -845,3 +869,11 @@ def non_zero_exit_code(self):
     @property
     def force(self):
         return self._get_argument_value("force", False, False)
+
+    @property
+    def templates_to_process(self):
+        return self._templates_to_process
+
+    @templates_to_process.setter
+    def templates_to_process(self, value: bool):
+        self._templates_to_process = value

src/cfnlint/decode/cfn_json.py

@@ -356,15 +356,13 @@ def load(filename):
 
     content = ""
 
-    if not sys.stdin.isatty():
-        filename = "-" if filename is None else filename
-        if sys.version_info.major <= 3 and sys.version_info.minor <= 9:
-            for line in fileinput.input(files=filename):
-                content = content + line
-        else:
-            for line in fileinput.input(  # pylint: disable=unexpected-keyword-arg
-                files=filename, encoding="utf-8"
-            ):
+    if (filename is None) and (not sys.stdin.isatty()):
+        filename = "-"  # no filename provided, it's stdin
+        fileinput_args = {"files": filename}
+        if sys.version_info.major <= 3 and sys.version_info.minor >= 10:
+            fileinput_args["encoding"] = "utf-8"
+        with fileinput.input(**fileinput_args) as f:
+            for line in f:
                 content = content + line
     else:
         with open(filename, encoding="utf-8") as fp:

src/cfnlint/decode/cfn_yaml.py

@@ -304,15 +304,13 @@ def load(filename):
 
     content = ""
 
-    if not sys.stdin.isatty():
-        filename = "-" if filename is None else filename
-        if sys.version_info.major <= 3 and sys.version_info.minor <= 9:
-            for line in fileinput.input(files=filename):
-                content = content + line
-        else:
-            for line in fileinput.input(  # pylint: disable=unexpected-keyword-arg
-                files=filename, encoding="utf-8"
-            ):
+    if (filename is None) and (not sys.stdin.isatty()):
+        filename = "-"  # no filename provided, it's stdin
+        fileinput_args = {"files": filename}
+        if sys.version_info.major <= 3 and sys.version_info.minor >= 10:
+            fileinput_args["encoding"] = "utf-8"
+        with fileinput.input(**fileinput_args) as f:
+            for line in f:
                 content = content + line
     else:
         with open(filename, encoding="utf-8") as fp:

src/cfnlint/runner.py

@@ -223,6 +223,7 @@ def __init__(self, config: ConfigMixIn) -> None:
                 settings for the template scan.
         """
         self.config = config
+        self.config.templates
         self.formatter = get_formatter(self.config)
         self.rules: Rules = Rules()
         self._get_rules()
@@ -388,7 +389,8 @@ def run(self) -> Iterator[Match]:
         Raises:
             None: This function does not raise any exceptions.
         """
-        if not sys.stdin.isatty() and not self.config.templates:
+
+        if (not sys.stdin.isatty()) and (not self.config.templates_to_process):
             yield from self._validate_filenames([None])
             return
 
@@ -434,7 +436,7 @@ def cli(self) -> None:
             print(self.rules)
             sys.exit(0)
 
-        if not self.config.templates:
+        if not self.config.templates_to_process:
             if sys.stdin.isatty():
                 self.config.parser.print_help()
                 sys.exit(1)

test/unit/module/config/test_config_mixin.py

@@ -198,18 +198,18 @@ def test_config_expand_paths(self, yaml_mock):
         )
 
     @patch("cfnlint.config.ConfigFileArgs._read_config", create=True)
-    def test_config_expand_paths_failure(self, yaml_mock):
+    def test_config_expand_paths_nomatch(self, yaml_mock):
         """Test precedence in"""
 
-        filename = "test/fixtures/templates/badpath/*.yaml"
+        filename = "test/fixtures/templates/nonexistant/*.yaml"
         yaml_mock.side_effect = [
-            {"templates": ["test/fixtures/templates/badpath/*.yaml"]},
+            {"templates": [filename]},
             {},
         ]
         config = cfnlint.config.ConfigMixIn([])
 
         # test defaults
-        self.assertEqual(config.templates, [str(Path(filename))])
+        self.assertEqual(config.templates, [])
 
     @patch("cfnlint.config.ConfigFileArgs._read_config", create=True)
     def test_config_expand_ignore_templates(self, yaml_mock):