Verify runpath does not contain a file

src/ert/config/model_config.py

@@ -3,6 +3,7 @@
 import contextlib
 import logging
 import os.path
+import re
 import shutil
 from pathlib import Path
 
@@ -25,6 +26,8 @@
 DEFAULT_JOBNAME_FORMAT = "<CONFIG_FILE>-<IENS>"
 DEFAULT_ECLBASE_FORMAT = "ECLBASE<IENS>"
 
+_TOKEN_REGEX = re.compile(r"<[^<>]+>")
+
 FULL_DISK_PERCENTAGE_THRESHOLD = 0.97
 MINIMUM_BYTES_LEFT_ON_DISK_THRESHOLD = 200 * 1000**3  # 200 GB
 # We give warning if free disk space is less than MINIMUM_BYTES_LEFT_ON_DISK_THRESHOLD
@@ -74,6 +77,9 @@ def validate_runpath(cls, runpath_format_string: str) -> str:
             )
             ConfigWarning.warn(msg)
             logger.warning(msg)
+
+        cls._validate_static_parts_exists(result)
+
         with contextlib.suppress(Exception):
             mount_dir = get_mount_directory(Path(runpath_format_string))
             total_space, used_space, free_space = shutil.disk_usage(mount_dir)
@@ -127,6 +133,35 @@ def from_dict(cls, config_dict: ConfigDict) -> ModelConfig:
             ),
         )
 
+    @staticmethod
+    def _validate_static_parts_exists(runpath_format: str) -> None:
+        """
+        Splits the provided runpath format into parts
+        and verifies that the static prefix, if present,
+        consists of directories.
+
+        Static parts after dynamic parts are not validated,
+        as dynamic parts are resolved later in the application.
+        """
+
+        parts = Path(runpath_format).parts
+
+        static_parts = []
+        for part in parts:
+            if _TOKEN_REGEX.search(part):
+                break
+            static_parts.append(part)
+
+        if not static_parts:
+            return
+
+        static_dir = Path(*static_parts)
+        if static_dir.exists() and not static_dir.is_dir():
+            raise ConfigValidationError(
+                f"Invalid runpath format; {static_dir} exists, but is not a directory."
+            )
+        return
+
 
 def _replace_runpath_format(format_string: str) -> str:
     format_string = format_string.replace("%d", "<IENS>", 1)

tests/ert/unit_tests/config/test_model_config.py

@@ -57,6 +57,25 @@ def test_model_config_jobname_and_eclbase(extra_config, expected):
     assert ModelConfig.from_dict(config_dict).jobname_format_string == expected
 
 
+def test_that_runpath_validation_raises_error_when_static_prefix_is_not_a_dir(tmp_path):
+    file = tmp_path / "not_a_dir"
+    file.write_text("This is a file")
+
+    with pytest.raises(ValueError, match="not a directory"):
+        ModelConfig(runpath_format_string=str(file / "<IENS>" / "<ITER>"))
+
+
+def test_that_runpath_validation_does_not_raise_error_when_static_prefix_is_a_dir(
+    tmp_path,
+):
+    static_dir = tmp_path / "dir"
+    static_dir.mkdir()
+
+    ModelConfig(
+        runpath_format_string=str(static_dir / "<IENS>" / "static_part" / "<ITER>")
+    )
+
+
 @pytest.mark.parametrize(
     ("total_space", "used_space", "to_warn", "expected_warning"),
     [