Add backend option help

.pre-commit-config.yaml

@@ -32,5 +32,5 @@ repos:
   rev: v2.17.0
   hooks:
   - id: pylint
-    additional_dependencies: [click,dataclasses_json,httpx,lorem-text,'textual>=0.18.0',websockets,tiktoken]
+    additional_dependencies: [click,dataclasses_json,httpx,lorem-text,simple-parsing,'textual>=0.18.0',tiktoken,websockets]
     args: ['--source-roots', 'src']

pyproject.toml

@@ -26,6 +26,7 @@ dependencies = [
     "httpx",
     "lorem-text",
     "platformdirs",
+    "simple_parsing",
     "textual>=0.18.0",
     "tiktoken",
     "websockets",

src/chap/backends/lorem.py

@@ -22,9 +22,13 @@ class Lorem:
     @dataclass
     class Parameters:
         delay_mu: float = 0.035
+        """Average delay between tokens"""
         delay_sigma: float = 0.02
+        """Standard deviation of token delay"""
         paragraph_lo: int = 1
+        """Minimum response paragraph count"""
         paragraph_hi: int = 5
+        """Maximum response paragraph count (inclusive)"""
 
     def __init__(self):
         self.parameters = self.Parameters()

src/chap/backends/openai_chatgpt.py

@@ -72,6 +72,7 @@ class ChatGPT:
     @dataclass
     class Parameters:
         model: str = "gpt-3.5-turbo"
+        """The model to use. The most common alternative value is 'gpt-4'."""
 
         max_request_tokens: int = 1024
         """The approximate greatest number of tokens to send in a request. When the session is long, the system prompt and 1 or more of the most recent interaction steps are sent."""

src/chap/core.py

@@ -8,10 +8,11 @@ import importlib
 import pathlib
 import pkgutil
 import subprocess
-from dataclasses import dataclass, fields
+from dataclasses import MISSING, dataclass, fields
 
 import click
 import platformdirs
+from simple_parsing.docstring import get_attribute_docstring
 
 from . import commands  # pylint: disable=no-name-in-module
 from .session import Session
@@ -88,7 +89,33 @@ def set_system_message(ctx, param, value):  # pylint: disable=unused-argument
 
 
 def set_backend(ctx, param, value):  # pylint: disable=unused-argument
-    ctx.obj.api = get_api(value)
+    try:
+        ctx.obj.api = get_api(value)
+    except ModuleNotFoundError as e:
+        raise click.BadParameter(str(e))
+
+
+def backend_help(ctx, param, value):  # pylint: disable=unused-argument
+    if ctx.resilient_parsing or not value:
+        return
+
+    if ctx.obj.api is None:
+        set_backend(ctx, "--backend", "chatgpt")
+
+    api = ctx.obj.api
+    if not hasattr(api, "parameters"):
+        click.utils.echo(f"{api.__class__.__name__} does not support parameters")
+    else:
+        click.utils.echo(f"{api.__class__.__name__} accepts the following parameters")
+        for f in fields(api.parameters):
+            default = f.default if f.default_factory is MISSING else f.default_factory()
+            doc = get_attribute_docstring(type(api.parameters), f.name).docstring_below
+            newline_doc = f"\n    {doc}" if doc else ""
+            click.utils.echo(
+                f"""\
+-B {f.name}:{f.type.__name__} (default: {default}){newline_doc}"""
+            )
+    ctx.exit()
 
 
 def set_backend_option(ctx, param, opts):  # pylint: disable=unused-argument
@@ -155,6 +182,14 @@ def uses_new_session(f):
         expose_value=False,
         is_eager=True,
     )(f)
+    f = click.option(
+        "--backend-help",
+        is_flag=True,
+        is_eager=True,
+        callback=backend_help,
+        expose_value=False,
+        help="Show information about backend options",
+    )(f)
     f = click.option(
         "--backend-option",
         "-B",