Tiled=true fails silently

tiled_assert.py

#!/usr/bin/env python
from pprint import pprint
from functools import reduce
import operator

import numpy as np

from affine import Affine
from rasterio.crs import CRS
import rasterio


image_shape = (4, 128, 128)
blocksizes = (128, 128)
size = reduce(operator.mul, image_shape, 1)

arr = (
    np.random.randint(low=-0, high=255, size=size)
    .astype("uint8")
    .reshape(image_shape)
)

options = {
    "driver": "GTiff",
    "dtype": "uint8",
    "nodata": None,
    "count": image_shape[0],
    "width": image_shape[1],
    "height": image_shape[2],
    "crs": CRS({"init": "epsg:3857"}),
    "transform": Affine(600, 0.0, -20037508, 0.0, -600, -939258),
    "tiled": True,
    "compress": "JPEG",
    "interleave": "pixel",
    "blockxsize": blocksizes[0],
    "blockysize": blocksizes[1],
}


with rasterio.open('/tmp/out.tif', 'w', **options) as dst:
    dst.write(arr)

with rasterio.open('/tmp/out.tif', 'r') as test_src:
    pprint(test_src.profile)
    assert test_src.is_tiled

Results when the image shape dimensions are less than blocksize (error)

Traceback (most recent call last):
  File "tiled_assert.py", line 40, in <module>
    with rasterio.open('/tmp/out.tif', 'w', **options) as dst:
  File "/Users/mperry/env/pxm/lib/python3.6/site-packages/rasterio/__init__.py", line 230, in open
    **kwargs)
  File "rasterio/_io.pyx", line 1010, in rasterio._io.DatasetWriterBase.__init__
ValueError: blockxsize exceeds raster width.

Results when the image dimensions are equal to blocksize (silently ignore geotiff tiling)

{'compress': 'jpeg',
 'count': 4,
 'crs': CRS({'init': 'epsg:3857'}),
 'driver': 'GTiff',
 'dtype': 'uint8',
 'height': 128,
 'interleave': 'pixel',
 'nodata': None,
 'tiled': False,
 'transform': Affine(600.0, 0.0, -20037508.0,
       0.0, -600.0, -939258.0),
 'width': 128}
Traceback (most recent call last):
  File "tiled_assert.py", line 45, in <module>
    assert test_src.is_tiled
AssertionError

Only when the image dimensions are greater than the blocksize does the assertion of internally tiled output hold.