feat(cli): add --json flag to flask routes command

Adds a machine-readable output mode to `flask routes`. When --json is
passed, the route table is emitted as a JSON array instead of the text
table. Each entry has `endpoint`, `methods` (sorted list), and `rule`;
subdomain apps also emit `subdomain`, host-matching apps emit `host`.
HEAD/OPTIONS are filtered unless --all-methods is also passed. Empty
apps produce `[]`. The --sort flag is honoured in JSON mode.

Backwards compatible: the flag is optional and all existing invocations
of `flask routes` are unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CHANGES.rst

@@ -3,6 +3,8 @@ Version 3.2.0
 
 Unreleased
 
+-   The ``flask routes`` command has a ``--json`` flag to output the route
+    table as a JSON array, suitable for scripting and tooling.
 -   Drop support for Python 3.9. :pr:`5730`
 -   Remove previously deprecated code: ``__version__``. :pr:`5648`
 -   ``RequestContext`` has merged with ``AppContext``. ``RequestContext`` is now

src/flask/cli.py

@@ -4,6 +4,7 @@ import ast
 import collections.abc as cabc
 import importlib.metadata
 import inspect
+import json
 import os
 import platform
 import re
@@ -1057,18 +1058,57 @@ def shell_command() -> None:
     ),
 )
 @click.option("--all-methods", is_flag=True, help="Show HEAD and OPTIONS methods.")
+@click.option("--json", "output_json", is_flag=True, help="Output routes as JSON.")
 @with_appcontext
-def routes_command(sort: str, all_methods: bool) -> None:
-    """Show all registered routes with endpoints and methods."""
+def routes_command(sort: str, all_methods: bool, output_json: bool) -> None:
+    """Show all registered routes with endpoints and methods.
+
+    :param sort: Column to sort by.
+    :param all_methods: Include HEAD and OPTIONS in the methods column.
+    :param output_json: Emit JSON instead of a text table.
+
+    .. versionchanged:: 3.2
+        Added the ``--json`` flag.
+    """
     rules = list(current_app.url_map.iter_rules())
+    ignored_methods = set() if all_methods else {"HEAD", "OPTIONS"}
+    host_matching = current_app.url_map.host_matching
+    has_domain = any(rule.host if host_matching else rule.subdomain for rule in rules)
+
+    if output_json:
+        data: list[dict[str, t.Any]] = []
+
+        for rule in rules:
+            entry: dict[str, t.Any] = {
+                "endpoint": rule.endpoint,
+                "methods": sorted((rule.methods or set()) - ignored_methods),
+                "rule": rule.rule,
+            }
+
+            if has_domain:
+                if host_matching:
+                    entry["host"] = rule.host or ""
+                else:
+                    entry["subdomain"] = rule.subdomain or ""
+
+            data.append(entry)
+
+        sort_key_map: dict[str, t.Callable[[dict[str, t.Any]], str]] = {
+            "endpoint": lambda e: e["endpoint"],
+            "methods": lambda e: ", ".join(e["methods"]),
+            "domain": lambda e: e.get("host", e.get("subdomain", "")),
+            "rule": lambda e: e["rule"],
+        }
+        if sort in sort_key_map:
+            data.sort(key=sort_key_map[sort])
+
+        click.echo(json.dumps(data, indent=2))
+        return
 
     if not rules:
         click.echo("No routes were registered.")
         return
 
-    ignored_methods = set() if all_methods else {"HEAD", "OPTIONS"}
-    host_matching = current_app.url_map.host_matching
-    has_domain = any(rule.host if host_matching else rule.subdomain for rule in rules)
     rows = []
 
     for rule in rules:

tests/test_cli.py

@@ -1,6 +1,7 @@
 # This file was part of Flask-CLI and was modified under the terms of
 # its Revised BSD License. Copyright © 2015 CERN.
 import importlib.metadata
+import json
 import os
 import platform
 import ssl
@@ -518,6 +519,78 @@ class TestRoutes:
         assert result.exit_code == 0
         assert "Host" in result.output
 
+    def test_json_output(self, invoke):
+        result = invoke(["routes", "--json"])
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        assert isinstance(data, list)
+        endpoints = {r["endpoint"] for r in data}
+        assert "yyy_get_post" in endpoints
+        assert "aaa_post" in endpoints
+        for route in data:
+            assert "endpoint" in route
+            assert "methods" in route
+            assert "rule" in route
+            assert isinstance(route["methods"], list)
+
+    def test_json_no_routes(self, runner):
+        app = Flask(__name__, static_folder=None)
+        cli = FlaskGroup(create_app=lambda: app)
+        result = runner.invoke(cli, ["routes", "--json"])
+        assert result.exit_code == 0
+        assert json.loads(result.output) == []
+
+    def test_json_excludes_head_options_by_default(self, invoke):
+        result = invoke(["routes", "--json"])
+        data = json.loads(result.output)
+        for route in data:
+            assert "HEAD" not in route["methods"]
+            assert "OPTIONS" not in route["methods"]
+
+    def test_json_all_methods(self, invoke):
+        result = invoke(["routes", "--json", "--all-methods"])
+        data = json.loads(result.output)
+        get_post_route = next(r for r in data if r["endpoint"] == "yyy_get_post")
+        assert "HEAD" in get_post_route["methods"]
+        assert "OPTIONS" in get_post_route["methods"]
+
+    def test_json_with_subdomain(self, runner):
+        app = Flask(__name__, static_folder=None)
+        app.add_url_rule("/a", subdomain="a", endpoint="a")
+        cli = FlaskGroup(create_app=lambda: app)
+        result = runner.invoke(cli, ["routes", "--json"])
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        route_a = next(r for r in data if r["endpoint"] == "a")
+        assert route_a["subdomain"] == "a"
+
+    def test_json_with_host_matching(self, runner):
+        app = Flask(__name__, static_folder=None)
+        app.url_map.host_matching = True
+        app.add_url_rule("/a", host="example.com", endpoint="a")
+        cli = FlaskGroup(create_app=lambda: app)
+        result = runner.invoke(cli, ["routes", "--json"])
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        route_a = next(r for r in data if r["endpoint"] == "a")
+        assert route_a["host"] == "example.com"
+
+    @pytest.mark.parametrize("sort_key,extract", [
+        ("endpoint", lambda r: r["endpoint"]),
+        ("rule", lambda r: r["rule"]),
+    ])
+    def test_json_sort(self, invoke, sort_key, extract):
+        result = invoke(["routes", "--json", "-s", sort_key])
+        data = json.loads(result.output)
+        values = [extract(r) for r in data]
+        assert values == sorted(values)
+
+    def test_json_sort_match_preserves_iter_rules_order(self, app, invoke):
+        match_result = invoke(["routes", "--json", "-s", "match"])
+        data = json.loads(match_result.output)
+        expected_order = [rule.endpoint for rule in app.url_map.iter_rules()]
+        assert [r["endpoint"] for r in data] == expected_order
+
 
 def dotenv_not_available():
     try: