Rename choose_formatter back to choose_encoder

Temporarily keep an alias so that choose_formatter will work for the
0.14.x release cycle.

Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>

prometheus_client/exposition.py

@@ -13,6 +13,7 @@
 from urllib.request import (
     build_opener, HTTPHandler, HTTPRedirectHandler, Request,
 )
+import warnings
 from wsgiref.simple_server import make_server, WSGIRequestHandler, WSGIServer
 
 from .openmetrics import exposition as openmetrics
@@ -97,10 +98,10 @@ def redirect_request(self, req, fp, code, msg, headers, newurl):
 def _bake_output(registry, accept_header, accept_encoding_header, params, disable_compression):
     """Bake output for metrics output."""
     # Choose the correct plain text format of the output.
-    formatter, content_type = choose_formatter(accept_header)
+    encoder, content_type = choose_encoder(accept_header)
     if 'name[]' in params:
         registry = registry.restricted_registry(params['name[]'])
-    output = formatter(registry)
+    output = encoder(registry)
     headers = [('Content-Type', content_type)]
     # If gzip encoding required, gzip the output.
     if not disable_compression and gzip_accepted(accept_encoding_header):
@@ -237,7 +238,7 @@ def sample_line(line):
     return ''.join(output).encode('utf-8')
 
 
-def choose_formatter(accept_header: str) -> Tuple[Callable[[CollectorRegistry], bytes], str]:
+def choose_encoder(accept_header: str) -> Tuple[Callable[[CollectorRegistry], bytes], str]:
     accept_header = accept_header or ''
     for accepted in accept_header.split(','):
         if accepted.split(';')[0].strip() == 'application/openmetrics-text':
@@ -246,6 +247,15 @@ def choose_formatter(accept_header: str) -> Tuple[Callable[[CollectorRegistry],
     return generate_latest, CONTENT_TYPE_LATEST
 
 
+def choose_formatter(accept_header: str) -> Tuple[Callable[[CollectorRegistry], bytes], str]:
+    warnings.warn(
+        "choose_formatter is deprecated and will be removed in a future version, please use choose_encoder instead",
+        DeprecationWarning,
+        stacklevel=2
+    )
+    return choose_encoder(accept_header)
+
+
 def gzip_accepted(accept_encoding_header: str) -> bool:
     accept_encoding_header = accept_encoding_header or ''
     for accepted in accept_encoding_header.split(','):

tests/test_exposition.py

@@ -2,6 +2,7 @@
 import threading
 import time
 import unittest
+import warnings
 
 import pytest
 
@@ -12,9 +13,10 @@
 )
 from prometheus_client.core import GaugeHistogramMetricFamily, Timestamp
 from prometheus_client.exposition import (
-    basic_auth_handler, default_handler, MetricsHandler,
-    passthrough_redirect_handler,
+    basic_auth_handler, choose_encoder, choose_formatter, default_handler,
+    MetricsHandler, passthrough_redirect_handler,
 )
+import prometheus_client.openmetrics.exposition as openmetrics
 
 
 class TestGenerateText(unittest.TestCase):
@@ -460,5 +462,19 @@ def test_histogram_metric_families(MetricFamily, registry, buckets, sum_value, e
     _expect_metric_exception(registry, error)
 
 
+def test_choose_encoder():
+    assert choose_encoder(None) == (generate_latest, CONTENT_TYPE_LATEST)
+    assert choose_encoder(CONTENT_TYPE_LATEST) == (generate_latest, CONTENT_TYPE_LATEST)
+    assert choose_encoder(openmetrics.CONTENT_TYPE_LATEST) == (openmetrics.generate_latest, openmetrics.CONTENT_TYPE_LATEST)
+
+
+def test_choose_formatter():
+    with warnings.catch_warnings(record=True) as w:
+        assert choose_formatter('') == (generate_latest, CONTENT_TYPE_LATEST)
+        assert len(w) == 1
+        assert issubclass(w[-1].category, DeprecationWarning)
+        assert "choose_formatter is deprecated" in str(w[-1].message)
+
+
 if __name__ == '__main__':
     unittest.main()