Wrap GMT_Inquire_VirtualFile to get the family of virtualfiles (#3152)

Co-authored-by: Yvonne Fröhlich <94163266+yvonnefroehlich@users.noreply.github.com>

pygmt/clib/session.py

@@ -1709,6 +1709,35 @@ def virtualfile_out(
             with self.open_virtualfile(family, geometry, "GMT_OUT", None) as vfile:
                 yield vfile
 
+    def inquire_virtualfile(self, vfname: str) -> int:
+        """
+        Get the family of a virtual file.
+
+        Parameters
+        ----------
+        vfname
+            Name of the virtual file to inquire.
+
+        Returns
+        -------
+        family
+            The integer value for the family of the virtual file.
+
+        Examples
+        --------
+        >>> from pygmt.clib import Session
+        >>> with Session() as lib:
+        ...     with lib.virtualfile_out(kind="dataset") as vfile:
+        ...         family = lib.inquire_virtualfile(vfile)
+        ...         assert family == lib["GMT_IS_DATASET"]
+        """
+        c_inquire_virtualfile = self.get_libgmt_func(
+            "GMT_Inquire_VirtualFile",
+            argtypes=[ctp.c_void_p, ctp.c_char_p],
+            restype=ctp.c_uint,
+        )
+        return c_inquire_virtualfile(self.session_pointer, vfname.encode())
+
     def read_virtualfile(
         self, vfname: str, kind: Literal["dataset", "grid", None] = None
     ):

pygmt/tests/test_clib_virtualfiles.py

@@ -379,3 +379,31 @@ def test_virtualfile_from_vectors_arraylike():
         bounds = "\t".join([f"<{min(i):.0f}/{max(i):.0f}>" for i in (x, y, z)])
         expected = f"<vector memory>: N = {size}\t{bounds}\n"
         assert output == expected
+
+
+def test_inquire_virtualfile():
+    """
+    Test that the inquire_virtualfile method returns the correct family.
+
+    Currently, only output virtual files are tested.
+    """
+    with clib.Session() as lib:
+        for family in [
+            "GMT_IS_DATASET",
+            "GMT_IS_DATASET|GMT_VIA_MATRIX",
+            "GMT_IS_DATASET|GMT_VIA_VECTOR",
+        ]:
+            with lib.open_virtualfile(
+                family, "GMT_IS_PLP", "GMT_OUT|GMT_IS_REFERENCE", None
+            ) as vfile:
+                assert lib.inquire_virtualfile(vfile) == lib["GMT_IS_DATASET"]
+
+        for family, geometry in [
+            ("GMT_IS_GRID", "GMT_IS_SURFACE"),
+            ("GMT_IS_IMAGE", "GMT_IS_SURFACE"),
+            ("GMT_IS_CUBE", "GMT_IS_VOLUME"),
+            ("GMT_IS_PALETTE", "GMT_IS_NONE"),
+            ("GMT_IS_POSTSCRIPT", "GMT_IS_NONE"),
+        ]:
+            with lib.open_virtualfile(family, geometry, "GMT_OUT", None) as vfile:
+                assert lib.inquire_virtualfile(vfile) == lib[family]