Repository: streamlink/streamlink

Issue:
--show-matchers fails with lazy plugin loading
### Checklist

- [x] This is a bug report and not [a different kind of issue](https://github.com/streamlink/streamlink/issues/new/choose)
- [x] [I have read the contribution guidelines](https://github.com/streamlink/streamlink/blob/master/CONTRIBUTING.md#contributing-to-streamlink)
- [x] [I have checked the list of open and recently closed bug reports](https://github.com/streamlink/streamlink/issues?q=is%3Aissue+label%3A%22bug%22)
- [x] [I have checked the commit log of the master branch](https://github.com/streamlink/streamlink/commits/master)

### Collaboration

- [x] [I will provide feedback should a pull request be opened with a fix for the problem](https://github.com/streamlink/streamlink/blob/master/CONTRIBUTING.md#pull-request-feedback)

### Streamlink version

7.1.0

### Description

No idea why I didn't check that before tagging 7.1.0, but the newly added `--show-matchers` CLI argument (#6287) doesn't work if plugins are loaded lazily, namely in all regular installs. Editable installs (`pip install -e .`) always load all plugins, which is why this slipped through. The added tests also didn't make me aware of this. Annoying...

```
$ streamlink --show-matchers=twitch
error: Plugin not found
```

```
$ streamlink twitch.tv/channel --show-matchers=twitch
- name: player
  pattern: https?://player\.twitch\.tv/\?.+
- name: clip
  pattern: https?://(?:clips\.twitch\.tv|(?:[\w-]+\.)?twitch\.tv/(?:[\w-]+/)?clip)/(?P<clip_id>[^/?]+)
- name: vod
  pattern: https?://(?:[\w-]+\.)?twitch\.tv/(?:[\w-]+/)?v(?:ideos?)?/(?P<video_id>\d+)
- name: live
  pattern: https?://(?:(?!clips\.)[\w-]+\.)?twitch\.tv/(?P<channel>(?!v(?:ideos?)?/|clip/)[^/?]+)/?(?:\?|$)
```


### Debug log

```text
.
```

Discussion:

Patch:
diff --git a/src/streamlink_cli/show_matchers.py b/src/streamlink_cli/show_matchers.py
index 9b0798cd..78672c3c 100644
--- a/src/streamlink_cli/show_matchers.py
+++ b/src/streamlink_cli/show_matchers.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 import re
 from textwrap import dedent, indent
 
-from streamlink.plugin import HIGH_PRIORITY, LOW_PRIORITY, NO_PRIORITY, NORMAL_PRIORITY, Plugin
+from streamlink.plugin.plugin import HIGH_PRIORITY, LOW_PRIORITY, NO_PRIORITY, NORMAL_PRIORITY, Matchers
 from streamlink.session import Streamlink
 from streamlink_cli.console import ConsoleOutput
 from streamlink_cli.exceptions import StreamlinkCLIError
@@ -24,21 +24,23 @@ PATTERN_FLAG_NAMES: dict[int, str] = {
 
 
 def show_matchers(session: Streamlink, console: ConsoleOutput, pluginname: str):
-    if pluginname not in session.plugins:
+    available = dict(session.plugins.iter_matchers())
+
+    if pluginname not in available:
         raise StreamlinkCLIError("Plugin not found", code=1)
 
-    plugin = session.plugins[pluginname]
+    matchers = available[pluginname]
 
     if console.json:
-        console.msg_json(show_matchers_json(plugin))
+        console.msg_json(show_matchers_json(matchers))
     else:
-        console.msg(show_matchers_text(plugin))
+        console.msg(show_matchers_text(matchers))
 
 
-def show_matchers_text(plugin: type[Plugin]) -> str:
+def show_matchers_text(matchers: Matchers) -> str:
     output = []
     indentation = "  "
-    for matcher in plugin.matchers or []:
+    for matcher in matchers or []:
         data = []
         flags = [name for val, name in PATTERN_FLAG_NAMES.items() if matcher.pattern.flags & val]
         if matcher.name:
@@ -57,7 +59,7 @@ def show_matchers_text(plugin: type[Plugin]) -> str:
     return "\n".join(output)
 
 
-def show_matchers_json(plugin: type[Plugin]) -> list[dict]:
+def show_matchers_json(matchers: Matchers) -> list[dict]:
     return [
         {
             "name": matcher.name,
@@ -69,5 +71,5 @@ def show_matchers_json(plugin: type[Plugin]) -> list[dict]:
                 else matcher.pattern.pattern
             ),
         }
-        for matcher in plugin.matchers or []
+        for matcher in matchers or []
     ]  # fmt: skip


Test patch:
diff --git a/tests/cli/main/test_show_matchers.py b/tests/cli/main/test_show_matchers.py
index a7e8b14b..eb1529a7 100644
--- a/tests/cli/main/test_show_matchers.py
+++ b/tests/cli/main/test_show_matchers.py
@@ -6,7 +6,9 @@ from textwrap import dedent
 import pytest
 
 import streamlink_cli.main
-from streamlink.plugin import HIGH_PRIORITY, NORMAL_PRIORITY, Plugin, pluginmatcher
+
+# noinspection PyProtectedMember
+from streamlink.plugin.plugin import HIGH_PRIORITY, NORMAL_PRIORITY, Matcher, Matchers, Plugin, pluginmatcher
 from streamlink.session import Streamlink
 
 
@@ -21,6 +23,11 @@ def session(session: Streamlink):
 
     session.plugins.update({"plugin": MyPlugin})
 
+    # noinspection PyProtectedMember
+    session.plugins._matchers["lazy"] = Matchers(
+        Matcher(re.compile(r"FOO"), priority=NORMAL_PRIORITY),
+    )
+
     return session
 
 
@@ -66,7 +73,14 @@ def test_plugin_not_found(capsys: pytest.CaptureFixture[str], argv: list[str], o
                     baz
                     qux
             """).lstrip(),
-            id="no-json",
+            id="non-lazy-no-json",
+        ),
+        pytest.param(
+            ["--show-matchers", "lazy"],
+            dedent("""
+                - pattern: FOO
+            """).lstrip(),
+            id="lazy-no-json",
         ),
         pytest.param(
             ["--show-matchers", "plugin", "--json"],
@@ -94,6 +108,20 @@ def test_plugin_not_found(capsys: pytest.CaptureFixture[str], argv: list[str], o
             """).lstrip(),
             id="json",
         ),
+        pytest.param(
+            ["--show-matchers", "lazy", "--json"],
+            dedent(f"""
+                [
+                  {{
+                    "name": null,
+                    "priority": {NORMAL_PRIORITY},
+                    "flags": 0,
+                    "pattern": "FOO"
+                  }}
+                ]
+            """).lstrip(),
+            id="non-lazy-json",
+        ),
     ],
     indirect=["argv"],
 )