don't add new behavior to netcdf4 backend

Author: ianhi

xarray/backends/common.py

@@ -867,10 +867,6 @@ def _is_likely_dap_url(url: str) -> bool:
 
     url_lower = url.lower()
 
-    # Check for explicit DAP protocol schemes - these definitively indicate a DAP service
-    if url_lower.startswith(("dap2://", "dap4://", "dap://")):
-        return True
-
     # For remote URIs, check for DAP server software path patterns
     if is_remote_uri(url_lower):
         dap_path_patterns = (

xarray/backends/netCDF4_.py

@@ -463,15 +463,6 @@ def open(
         if isinstance(filename, os.PathLike):
             filename = os.fspath(filename)
 
-        # Replace DAP protocol prefixes with https:// - netCDF4 library can't handle them
-        # These prefixes may be added by users to explicitly indicate DAP protocol
-        # Following pydap's convention, we convert to https://
-        # See: https://github.com/pydap/pydap/blob/0a2b0892611abaf0a9762ffd4f2f082cb8e497c2/src/pydap/handlers/dap.py#L103-L107
-        if isinstance(filename, str):
-            filename_lower = filename.lower()
-            if filename_lower.startswith(("dap2://", "dap4://")):
-                filename = "https://" + filename[7:]
-
         if isinstance(filename, IOBase):
             raise TypeError(
                 f"file objects are not supported by the netCDF4 backend: {filename}"
@@ -724,11 +715,6 @@ def _has_netcdf_ext(path: str | os.PathLike, is_remote: bool = False) -> bool:
             _, ext = os.path.splitext(path)
             return ext in {".nc", ".nc4", ".cdf"}
 
-        # Check for explicit DAP protocol indicators:
-        # 1. DAP scheme: dap2:// or dap4:// (case-insensitive, may not be recognized by is_remote_uri)
-        # 2. Remote URI with /dap2/ or /dap4/ in URL path (case-insensitive)
-        # Note: We intentionally do NOT check for .dap suffix as that would match
-        # file extensions like .dap which trigger downloads of binary data
         if isinstance(filename_or_obj, str):
             url_lower = filename_or_obj.lower()
             from xarray.backends.common import _is_likely_dap_url

xarray/backends/pydap_.py

@@ -212,6 +212,9 @@ class PydapBackendEntrypoint(BackendEntrypoint):
     def guess_can_open(self, filename_or_obj: T_PathFileOrDataStore) -> bool:
         if not isinstance(filename_or_obj, str):
             return False
+        # Check for explicit DAP protocol schemes - these definitively indicate a DAP service
+        if filename_or_obj.lower().startswith(("dap2://", "dap4://", "dap://")):
+            return True
 
         return _is_likely_dap_url(filename_or_obj)