followups for JSON output formats

 * formats must be _registered_, or they aren't available for use in
   client software
 * make JSON formats able to encode Decimal values, emitting floats
 * make JSON formats able to encode None/NULL values, emitting nulls

Author: rolandwalker

CHANGELOG

@@ -1,5 +1,8 @@
 # Changelog
 
+- Register the JSON formats so they are actually usable.
+- Make JSON formats able to encode Decimals and None/NULLs.
+	
 ## Version 2.5.0
 
 - Added noheader CSV and TSV output formats.

cli_helpers/tabular_output/json_output_adapter.py

@@ -1,13 +1,22 @@
 # -*- coding: utf-8 -*-
 """A JSON data output adapter"""
 
+from decimal import Decimal
 from itertools import chain
 import json
 
-from .preprocessors import bytes_to_string, override_missing_value, convert_to_string
+from .preprocessors import bytes_to_string
 
 supported_formats = ("jsonl", "jsonl_escaped")
-preprocessors = (override_missing_value, bytes_to_string, convert_to_string)
+preprocessors = (bytes_to_string,)
+
+
+class CustomEncoder(json.JSONEncoder):
+    def default(self, o):
+        if isinstance(o, Decimal):
+            return float(o)
+        else:
+            return super(CustomEncoder, self).default(o)
 
 
 def adapter(data, headers, table_format="jsonl", **_kwargs):
@@ -22,6 +31,7 @@ def adapter(data, headers, table_format="jsonl", **_kwargs):
     for row in chain(data):
         yield json.dumps(
             dict(zip(headers, row, strict=True)),
+            cls=CustomEncoder,
             separators=(",", ":"),
             ensure_ascii=ensure_ascii,
         )

cli_helpers/tabular_output/output_formatter.py

@@ -17,6 +17,7 @@
     vertical_table_adapter,
     tabulate_adapter,
     tsv_output_adapter,
+    json_output_adapter,
 )
 from decimal import Decimal
 
@@ -253,3 +254,14 @@ def format_output(data, headers, format_name, **kwargs):
         tsv_output_adapter.preprocessors,
         {"table_format": tsv_format, "missing_value": "", "max_field_width": None},
     )
+
+for json_format in json_output_adapter.supported_formats:
+    TabularOutputFormatter.register_new_formatter(
+        json_format,
+        json_output_adapter.adapter,
+        json_output_adapter.preprocessors,
+        {
+            "table_format": json_format,
+            "max_field_width": None,
+        },
+    )

tests/tabular_output/test_json_output_adapter.py

@@ -3,6 +3,8 @@
 
 from __future__ import unicode_literals
 
+from decimal import Decimal
+
 from cli_helpers.tabular_output import json_output_adapter
 
 
@@ -29,6 +31,28 @@ def test_unicode_with_jsonl():
     )
 
 
+def test_decimal_with_jsonl():
+    """Test that the jsonl wrapper can pass through Decimal values."""
+    data = [["ab\r\nc", 1], ["d", Decimal(4.56)]]
+    headers = ["letters", "number"]
+    output = json_output_adapter.adapter(iter(data), headers, table_format="jsonl")
+    assert (
+        "\n".join(output)
+        == """{"letters":"ab\\r\\nc","number":1}\n{"letters":"d","number":4.56}"""
+    )
+
+
+def test_null_with_jsonl():
+    """Test that the jsonl wrapper can pass through null values."""
+    data = [["ab\r\nc", None], ["d", None]]
+    headers = ["letters", "value"]
+    output = json_output_adapter.adapter(iter(data), headers, table_format="jsonl")
+    assert (
+        "\n".join(output)
+        == """{"letters":"ab\\r\\nc","value":null}\n{"letters":"d","value":null}"""
+    )
+
+
 def test_unicode_with_jsonl_esc():
     """Test that the jsonl_escaped wrapper JSON-escapes non-ascii characters."""
     data = [["观音", 1], ["Ποσειδῶν", 456]]

tests/tabular_output/test_output_formatter.py

@@ -177,6 +177,13 @@ def test_unsupported_format():
         formatter.format_output((), (), format_name="foobar")
 
 
+def test_supported_json_formats():
+    """Test that the JSONl formats are known."""
+    formatter = TabularOutputFormatter()
+    assert "jsonl" in formatter.supported_formats
+    assert "jsonl_escaped" in formatter.supported_formats
+
+
 def test_tabulate_ansi_escape_in_default_value():
     """Test that ANSI escape codes work with tabulate."""