experiments: add --show-json for exp show (#4689)

dvc/command/experiments.py

@@ -3,7 +3,7 @@ import io
 import logging
 import os
 from collections import OrderedDict
-from datetime import date
+from datetime import date, datetime
 from itertools import groupby
 from typing import Iterable, Optional
 
@@ -255,6 +255,12 @@ def _show_experiments(all_experiments, console, **kwargs):
     console.print(table)
 
 
+def _format_json(item):
+    if isinstance(item, (date, datetime)):
+        return item.isoformat()
+    raise TypeError
+
+
 class CmdExperimentsShow(CmdBase):
     def run(self):
         from rich.console import Console
@@ -272,6 +278,12 @@ class CmdExperimentsShow(CmdBase):
                 sha_only=self.args.sha,
             )
 
+            if self.args.show_json:
+                import json
+
+                logger.info(json.dumps(all_experiments, default=_format_json))
+                return 0
+
             if self.args.no_pager:
                 console = Console()
             else:
@@ -530,6 +542,12 @@ def add_parser(subparsers, parent_parser):
         default=False,
         help="Always show git commit SHAs instead of branch/tag names.",
     )
+    experiments_show_parser.add_argument(
+        "--show-json",
+        action="store_true",
+        default=False,
+        help="Print output in JSON format instead of a human-readable table.",
+    )
     experiments_show_parser.set_defaults(func=CmdExperimentsShow)
 
     EXPERIMENTS_CHECKOUT_HELP = "Checkout experiments."