llm fragments loaders, closes #941

docs/fragments.md

@@ -146,3 +146,26 @@ Running `llm logs -c` will show that this prompt incorporated 26 fragments, one
 Running `llm logs -c --usage --expand` includes token usage information and turns each fragment ID into a full copy of that file. [Here's the output of that command](https://gist.github.com/simonw/c9bbbc5f6560b01f4b7882ac0194fb25).
 
 See the {ref}`register_fragment_loaders() plugin hook <plugin-hooks-register-fragment-loaders>` documentation for details on writing your own custom fragment plugin.
+
+(fragments-loaders)=
+## Listing available fragment prefixes
+
+The `llm fragments loaders` command shows all prefixes that have been installed by plugins, along with their documentation:
+
+```bash
+llm install llm-fragments-github
+llm fragments loaders
+```
+Example output:
+```
+github:
+  Load files from a GitHub repository as fragments.
+
+  Argument is a GitHub repository URL or username/repository
+
+issue:
+  Fetch GitHub issue and comments as Markdown
+
+  argument is either "owner/repo/NUMBER"
+  or "https://github.com/owner/repo/issues/NUMBER"
+```

docs/help.md

@@ -688,10 +688,11 @@ Options:
   --help  Show this message and exit.
 
 Commands:
-  list*   List current fragments
-  remove  Remove a fragment alias
-  set     Set an alias for a fragment
-  show    Display the fragment stored under an alias or hash
+  list*    List current fragments
+  loaders  Show fragment loaders registered by plugins
+  remove   Remove a fragment alias
+  set      Set an alias for a fragment
+  show     Display the fragment stored under an alias or hash
 ```
 
 (help-fragments-list)=
@@ -753,6 +754,17 @@ Options:
   --help  Show this message and exit.
 ```
 
+(help-fragments-loaders)=
+#### llm fragments loaders --help
+```
+Usage: llm fragments loaders [OPTIONS]
+
+  Show fragment loaders registered by plugins
+
+Options:
+  --help  Show this message and exit.
+```
+
 (help-plugins)=
 ### llm plugins --help
 ```

llm/cli.py

@@ -2283,6 +2283,26 @@ def fragments_remove(alias):
         )
 
 
+@fragments.command(name="loaders")
+def fragments_loaders():
+    """Show fragment loaders registered by plugins"""
+    from llm import get_fragment_loaders
+
+    found = False
+    for prefix, loader in get_fragment_loaders().items():
+        if found:
+            # Extra newline on all after the first
+            click.echo("")
+        found = True
+        docs = "Undocumented"
+        if loader.__doc__:
+            docs = textwrap.dedent(loader.__doc__).strip()
+        click.echo(f"{prefix}:")
+        click.echo(textwrap.indent(docs, "  "))
+    if not found:
+        click.echo("No fragment loaders found")
+
+
 @cli.command(name="plugins")
 @click.option("--all", help="Include built-in default plugins", is_flag=True)
 def plugins_list(all):

tests/test_plugins.py

@@ -94,6 +94,7 @@ def test_register_fragment_loaders(logs_db):
     assert get_fragment_loaders() == {}
 
     def single_fragment(argument):
+        "This is the fragment documentation"
         return llm.Fragment("single", "single")
 
     def three_fragments(argument):
@@ -127,6 +128,18 @@ def test_register_fragment_loaders(logs_db):
         assert result.exit_code == 0
         expected = "prompt:\n" "one:x\n" "two:x\n" "three:x\n"
         assert expected in result.output
+        # And the llm fragments loaders command:
+        result2 = runner.invoke(cli.cli, ["fragments", "loaders"])
+        assert result2.exit_code == 0
+        expected2 = (
+            "single:\n"
+            "  This is the fragment documentation\n"
+            "\n"
+            "three:\n"
+            "  Undocumented\n"
+        )
+        assert result2.output == expected2
+
     finally:
         plugins.pm.unregister(name="FragmentLoadersPlugin")
         assert get_fragment_loaders() == {}