silently allow .gz and .fz extesion when mapping

python/lsst/obs/base/mapping.py

@@ -126,9 +126,19 @@ def map(self, mapper, dataId, write=False):
         if not os.path.isabs(path):
             path = os.path.join(self.root, path)
         if not write:
-            newPath = mapper._parentSearch(path)
-            if newPath:
-                path = newPath
+            for ext in (None, '.gz', '.fz'):
+                if path.endswith(ext):
+                    continue # if the path already ends with the extension
+                extPath = path + ext if ext else path
+                newPath = mapper._parentSearch(extPath)
+                if newPath:
+                    path = newPath
+                    break
+                # This allows mapped files to be compressed, ending in .gz, without any indication from the
+                # policy that the file should be compressed. This allows repositories to contain a combination
+                # of comporessed and not-compressed files.
+                # If needed we can add a policy flag to allow compressed files or not, and perhaps a list of
+                # allowed extensions that may exist at the end of the template.
         assert path, "Fully-qualified filename is empty."
 
         addFunc = "add_" + self.datasetType  # Name of method for additionalData

tests/MinMapper2.paf

@@ -35,6 +35,18 @@ images: {
         persistable: "ImageF"
         tables:      raw
     }
+    someGz: {
+        template:    "gz/bar-%(ccd)02d.fits" # the file will end in ...fits.gz but butler will still find it.
+        python:      "lsst.afw.image.ExposureF"
+        persistable: "ExposureF"
+        tables:      raw
+    }
+        someFz: {
+        template:    "fz/bar-%(ccd)02d.fits" # the file will end in ...fits.fz but butler will still find it.
+        python:      "lsst.afw.image.ExposureF"
+        persistable: "ExposureF"
+        tables:      raw
+    }
 }
 calibrations: {
     flat: {