Fix file handle leaks in DFS/DFSU readers and generic functions

src/mikeio/dfs/_dfs1.py

@@ -87,10 +87,11 @@ class Dfs1(_Dfs123):
     def __init__(self, filename: str | Path) -> None:
         super().__init__(filename)
 
-        self._dfs = DfsFileFactory.Dfs1FileOpen(str(filename))
-        self._x0: float = self._dfs.SpatialAxis.X0
-        self._dx: float = self._dfs.SpatialAxis.Dx
-        self._nx: int = self._dfs.SpatialAxis.XCount
+        dfs = DfsFileFactory.Dfs1FileOpen(str(filename))
+        self._x0: float = dfs.SpatialAxis.X0
+        self._dx: float = dfs.SpatialAxis.Dx
+        self._nx: int = dfs.SpatialAxis.XCount
+        dfs.Close()
 
         origin = self._longitude, self._latitude
         self._geometry = Grid1D(

src/mikeio/dfs/_dfs3.py

@@ -138,21 +138,20 @@ def __init__(self, filename: str | Path):
         )
 
     def _read_dfs3_header(self, read_x0y0z0: bool = False) -> None:
-        self._dfs = DfsFileFactory.Dfs3FileOpen(self._filename)
-
-        self._source = self._dfs
+        dfs = DfsFileFactory.Dfs3FileOpen(self._filename)
 
         if read_x0y0z0:
-            self._x0 = self._dfs.SpatialAxis.X0
-            self._y0 = self._dfs.SpatialAxis.Y0
-            self._z0 = self._dfs.SpatialAxis.Z0
-
-        self._dx = self._dfs.SpatialAxis.Dx
-        self._dy = self._dfs.SpatialAxis.Dy
-        self._dz = self._dfs.SpatialAxis.Dz
-        self._nx = self._dfs.SpatialAxis.XCount
-        self._ny = self._dfs.SpatialAxis.YCount
-        self._nz = self._dfs.SpatialAxis.ZCount
+            self._x0 = dfs.SpatialAxis.X0
+            self._y0 = dfs.SpatialAxis.Y0
+            self._z0 = dfs.SpatialAxis.Z0
+
+        self._dx = dfs.SpatialAxis.Dx
+        self._dy = dfs.SpatialAxis.Dy
+        self._dz = dfs.SpatialAxis.Dz
+        self._nx = dfs.SpatialAxis.XCount
+        self._ny = dfs.SpatialAxis.YCount
+        self._nz = dfs.SpatialAxis.ZCount
+        dfs.Close()
 
     def read(
         self,

src/mikeio/dfsu/_dfsu.py

@@ -572,6 +572,7 @@ def _dfs_read_item_time_func(
     ) -> tuple[np.ndarray, pd.Timestamp]:
         dfs = DfsuFile.Open(self._filename)
         itemdata = dfs.ReadItemTimeStep(item + 1, step)
+        dfs.Close()
 
         return itemdata.Data, itemdata.Time
 

src/mikeio/generic.py

@@ -819,6 +819,8 @@ def avg_time(
             outdatalist[item][has_value] += d[has_value]
             steps_list[item][has_value] += 1
 
+    dfs_i.Close()
+
     for item in range(n_items):
         darray = np.zeros_like(outdatalist[item], dtype=np.float32)
         if skipna:
@@ -945,6 +947,8 @@ def quantile(
         # TODO should this be static Z coordinates instead?
         dfs_o.WriteItemTimeStepNext(0.0, znitemdata.Data)
 
+    dfs_i.Close()
+
     for item in range(n_items_out):
         darray = outdatalist[item].astype(np.float32)
         dfs_o.WriteItemTimeStepNext(0.0, darray)

tests/test_file_handle_close.py

@@ -0,0 +1,48 @@
+"""Tests verifying that file handles are properly closed after use."""
+
+import gc
+import os
+import platform
+
+import pytest
+
+import mikeio
+
+
+def _count_open_fds() -> int:
+    """Count open file descriptors on Linux via /proc/self/fd."""
+    return len(os.listdir("/proc/self/fd"))
+
+
+pytestmark = pytest.mark.skipif(
+    platform.system() != "Linux",
+    reason="File descriptor counting via /proc only works on Linux",
+)
+
+
+def test_dfs1_init_closes_file_handle() -> None:
+    gc.collect()
+    baseline = _count_open_fds()
+    for _ in range(50):
+        mikeio.Dfs1("tests/testdata/random.dfs1")
+    gc.collect()
+    assert _count_open_fds() - baseline == 0
+
+
+def test_dfs3_init_closes_file_handle() -> None:
+    gc.collect()
+    baseline = _count_open_fds()
+    for _ in range(50):
+        mikeio.Dfs3("tests/testdata/Grid1.dfs3")
+    gc.collect()
+    assert _count_open_fds() - baseline == 0
+
+
+def test_dfsu_read_closes_file_handle() -> None:
+    gc.collect()
+    baseline = _count_open_fds()
+    for _ in range(50):
+        dfs = mikeio.open("tests/testdata/HD2D.dfsu")
+        dfs.read()
+    gc.collect()
+    assert _count_open_fds() - baseline == 0