use simplejson to allow NaN/inf/-inf in JSON response

CHANGES.md

@@ -1,6 +1,11 @@
 # Release Notes
 
-## 0.3.10 (TBD)
+## 0.3.10 (2021-09-23)
+
+### titiler.core
+
+- add custom JSONResponse using [simplejson](https://simplejson.readthedocs.io/en/latest/) to allow NaN/inf/-inf values (ref: https://github.com/developmentseed/titiler/pull/374)
+- use `titiler.core.resources.responses.JSONResponse` as default response for `info`, `metadata`, `statistics` and `point` endpoints (ref: https://github.com/developmentseed/titiler/pull/374)
 
 ### titiler.application
 

docs/output_format.md

@@ -48,3 +48,23 @@ data, mask = data[0:-1], data[-1]
 ```
 
 Notebook: [Working_with_NumpyTile](examples/notebooks/Working_with_NumpyTile.ipynb)
+
+## JSONResponse
+
+Sometimes rio-tiler's responses can contain `NaN`, `Infinity` or `-Infinity` values (e.g for Nodata). Sadly there is no proper ways to encode those values in JSON or at least not all web client supports it.
+
+In  order to allow TiTiler to return valid responses we added a custom `JSONResponse` in `v0.3.10` which will automatically translate `float('nan')`, `float('inf')` and `float('-inf')` to `null` and thus avoid in valid JSON response.
+
+```python
+
+from fastapi import FastAPI
+from titiler.core.resources.responses import JSONResponse
+
+app = FastAPI(default_response_class=JSONResponse,)
+
+@app.get("/something")
+def return_something():
+    return float('nan')
+```
+
+This `JSONResponse` is used by default in `titiler` Tiler Factories where `NaN` are expected (`info`, `metadata`, `statistics` and `point` endpoints).

src/titiler/application/tests/routes/test_cog.py

@@ -476,3 +476,37 @@ def test_validate_cog(app, url):
     response = app.get(f"/cog/validate?url={os.path.join(DATA_DIR, 'cog.tif')}")
     assert response.status_code == 200
     assert response.json()["COG"]
+
+
+@patch("rio_tiler.io.cogeo.rasterio")
+def test_json_response_with_nan(rio, app):
+    """test /info endpoint."""
+    rio.open = mock_rasterio_open
+
+    response = app.get("/cog/info?url=https://myurl.com/cog_with_nan.tif")
+    assert response.status_code == 200
+    body = response.json()
+    assert body["dtype"] == "float32"
+    assert body["nodata_type"] == "Nodata"
+    assert body["nodata_value"] is None
+
+    response = app.get("/cog/info.geojson?url=https://myurl.com/cog_with_nan.tif")
+    assert response.status_code == 200
+    assert response.headers["content-type"] == "application/geo+json"
+    body = response.json()
+    assert body["geometry"]
+    assert body["properties"]["nodata_type"] == "Nodata"
+    assert body["properties"]["nodata_value"] is None
+
+    response = app.get("/cog/metadata?url=https://myurl.com/cog_with_nan.tif")
+    assert response.status_code == 200
+    body = response.json()
+    assert body["nodata_type"] == "Nodata"
+    assert body["nodata_value"] is None
+
+    response = app.get(
+        "/cog/point/79.80860440702253,21.852217086223234?url=https://myurl.com/cog_with_nan.tif"
+    )
+    assert response.status_code == 200
+    body = response.json()
+    assert body["values"][0] is None

src/titiler/core/setup.py

@@ -14,6 +14,7 @@
     "pydantic",
     "rasterio",
     "rio-tiler>=2.1,<2.2",
+    "simplejson",
     # Additional requirements for python 3.6
     "async_exit_stack>=1.0.1,<2.0.0;python_version<'3.7'",
     "async_generator>=1.10,<2.0.0;python_version<'3.7'",

src/titiler/core/titiler/core/factory.py

@@ -32,7 +32,7 @@
 from titiler.core.models.mapbox import TileJSON
 from titiler.core.models.OGC import TileMatrixSetList
 from titiler.core.resources.enums import ImageType, MediaType, OptionalHeader
-from titiler.core.resources.responses import GeoJSONResponse, XMLResponse
+from titiler.core.resources.responses import GeoJSONResponse, JSONResponse, XMLResponse
 from titiler.core.utils import Timer, bbox_to_feature, data_stats
 
 from fastapi import APIRouter, Body, Depends, Path, Query
@@ -204,6 +204,7 @@ def info(self):
             response_model=Info,
             response_model_exclude={"minzoom", "maxzoom", "center"},
             response_model_exclude_none=True,
+            response_class=JSONResponse,
             responses={200: {"description": "Return dataset's basic info."}},
         )
         def info(
@@ -255,6 +256,7 @@ def metadata(self):
             response_model=Metadata,
             response_model_exclude={"minzoom", "maxzoom", "center"},
             response_model_exclude_none=True,
+            response_class=JSONResponse,
             responses={200: {"description": "Return dataset's metadata."}},
         )
         def metadata(
@@ -542,6 +544,7 @@ def point(self):
 
         @self.router.get(
             r"/point/{lon},{lat}",
+            response_class=JSONResponse,
             responses={200: {"description": "Return a value for a point"}},
         )
         def point(
@@ -780,6 +783,7 @@ def statistics(self):
 
         @self.router.get(
             "/statistics",
+            response_class=JSONResponse,
             responses={
                 200: {
                     "content": {"application/json": {}},
@@ -920,6 +924,7 @@ def info(self):
             response_model=Dict[str, Info],
             response_model_exclude={"minzoom", "maxzoom", "center"},
             response_model_exclude_none=True,
+            response_class=JSONResponse,
             responses={
                 200: {
                     "description": "Return dataset's basic info or the list of available assets."
@@ -991,6 +996,7 @@ def metadata(self):
             response_model=Dict[str, Metadata],
             response_model_exclude={"minzoom", "maxzoom", "center"},
             response_model_exclude_none=True,
+            response_class=JSONResponse,
             responses={200: {"description": "Return dataset's metadata."}},
         )
         def metadata(
@@ -1041,6 +1047,7 @@ def info(self):
             response_model=Info,
             response_model_exclude={"minzoom", "maxzoom", "center"},
             response_model_exclude_none=True,
+            response_class=JSONResponse,
             responses={
                 200: {
                     "description": "Return dataset's basic info or the list of available bands."
@@ -1107,6 +1114,7 @@ def metadata(self):
             response_model=Metadata,
             response_model_exclude={"minzoom", "maxzoom", "center"},
             response_model_exclude_none=True,
+            response_class=JSONResponse,
             responses={200: {"description": "Return dataset's metadata."}},
         )
         def metadata(

src/titiler/core/titiler/core/resources/responses.py

@@ -1,14 +1,36 @@
 """Common response models."""
 
-from starlette.responses import JSONResponse, Response
+from typing import Any
 
+import simplejson as json
 
-class XMLResponse(Response):
+from starlette import responses
+
+
+class XMLResponse(responses.Response):
     """XML Response"""
 
     media_type = "application/xml"
 
 
+class JSONResponse(responses.JSONResponse):
+    """Custom JSON Response."""
+
+    def render(self, content: Any) -> bytes:
+        """Render JSON.
+
+        Same defaults as starlette.responses.JSONResponse.render but allow NaN to be replaced by null using simplejson
+        """
+        return json.dumps(
+            content,
+            ensure_ascii=False,
+            allow_nan=False,
+            indent=None,
+            ignore_nan=True,
+            separators=(",", ":"),
+        ).encode("utf-8")
+
+
 class GeoJSONResponse(JSONResponse):
     """GeoJSON Response"""