Change _CRS class to make WKT canonical (#1597)

* Refactor of _CRS class to make WKT canonical

* Finish work on making WKT canonical

Many test assertions needed update

* Accept {'init': 'EPSG:xxxx'}

Also removed commented code

* Restore previous rio-info behavior when there's an EPSG code

* Remove unneeded import

* Use from_proj4 in from_epsg

* Rewrite of _CRS to keep an OGRSpatialReferenceH (#1602)

* Rewrite of _CRS to keep an OGRSpatialReferenceH

Rewrite of CRS to use _CRS by composition, not inheritance

New OGRErr handling function exc_wrap_ogrerr

* Remove commented code

* Add back in the error stack check for ImportFromProj

Also fix up docstrings

CHANGES.txt

@@ -4,6 +4,8 @@ Changes
 Next
 ----
 
+- The _CRS class has been refactored so that a WKT representation, rather than PROJ4 representation, is the canonical form.
+
 - On entering a dataset context (DatasetBase.__enter__) a new anonymous GDAL
   environment is created if needed and is entered. This makes `with
   rasterio.open(...) as dataset:` roughly equivalent to `with

rasterio/_base.pyx

@@ -262,56 +262,19 @@ cdef class DatasetBase(object):
 
     def _handle_crswkt(self, wkt):
         """Return the GDAL dataset's stored CRS"""
-        cdef OGRSpatialReferenceH osr = NULL
-        cdef const char *auth_key = NULL
-        cdef const char *auth_val = NULL
-
-        if not wkt:
-            log.debug("No projection detected.")
-            return None
-
-        wkt_b = wkt.encode('utf-8')
-        cdef const char *wkt_c = wkt_b
-
-        try:
-
-            osr = exc_wrap_pointer(OSRNewSpatialReference(wkt_c))
-            log.debug("Got coordinate system")
-
-            retval = OSRAutoIdentifyEPSG(osr)
-
-            if retval > 0:
-                log.debug("Failed to auto identify EPSG: %d", retval)
-
-            else:
-                log.debug("Auto identified EPSG: %d", retval)
-
-                try:
-                    auth_key = OSRGetAuthorityName(osr, NULL)
-                    auth_val = OSRGetAuthorityCode(osr, NULL)
-
-                except CPLE_NotSupportedError as exc:
-                    log.debug("{}".format(exc))
-
-                if auth_key != NULL and auth_val != NULL:
-                    return CRS({'init': u'{}:{}'.format(auth_key.lower(), auth_val)})
-
+        # No dialect morphing, if the dataset was created using software
+        # "speaking" the Esri dialect, we will read Esri WKT.
+        if wkt:
             return CRS.from_wkt(wkt)
-
-        except CPLE_BaseError as exc:
-            raise CRSError("{}".format(exc))
-
-        finally:
-             _safe_osr_release(osr)
+        else:
+            return CRS()
 
     def read_crs(self):
         """Return the GDAL dataset's stored CRS"""
-        cdef const char *wkt_b = NULL
-
-        wkt_b = GDALGetProjectionRef(self._hds)
-        if wkt_b == NULL:
-            raise ValueError("Unexpected NULL spatial reference")
+        cdef const char *wkt_b = GDALGetProjectionRef(self.handle())
         wkt = wkt_b
+        if wkt == NULL:
+            raise ValueError("Unexpected NULL spatial reference")
         return self._handle_crswkt(wkt)
 
     def read_transform(self):
@@ -1328,6 +1291,7 @@ cdef OGRSpatialReferenceH _osr_from_crs(object crs) except NULL:
         if retval:
             _safe_osr_release(osr)
             raise CRSError("Invalid CRS: {!r}".format(crs))
+        exc_wrap_int(OSRMorphFromESRI(osr))
     except CPLE_BaseError as exc:
         _safe_osr_release(osr)
         raise CRSError(str(exc))

rasterio/_crs.pxd

@@ -0,0 +1,8 @@
+# _CRS class definition
+
+include "gdal.pxi"
+
+
+cdef class _CRS:
+
+    cdef OGRSpatialReferenceH _osr