gptel: Add arbitrary params to request

Provide a way to add arbitrary parameters to the `gptel-request'
payload.  This is required for customizing parameters that gptel
does not provide user options for.

Examples in #330, #415, #471.

This is done by adding a `:request-params' field to the backend
and the model.  This should be a plist whose key/value pairs are
the additional request parameters and their values.  In case of
conflict, the model-specific request-parameters override the
backend-specific ones, which override gptel's dynamically set user
options.  Valid parameters depend on the specific API being
queried, and can be found in the corresponding API documentation.

* gptel.el (gptel--merge-plists, gptel--model-request-params): Add
utility functions.

* gptel-openai.el (gptel-backend, gptel-make-openai,
gptel-make-azure, gptel-make-gpt4all, gptel--request-data): Add
request-params slot to `gptel-backend' and keyword to
`gptel-make-openai' and its derivatives.  Merge model and
backend-specific request parameters when sending a request.

* gptel-privategpt.el (gptel-make-privategpt): Add request-params
keyword.

* gptel-ollama.el (gptel-make-ollama, gptel--request-data): Add
request-params keywod to `gptel-make-ollama'.  Merge model and
backend-specific request parameters when sending a request.
Remove ad hoc value of :num_ctx used according to #330 -- this is
no longer needed as :num_ctx can be set explicitly when defining
the Ollama model or backend.

* gptel-kagi.el (gptel--request-data): Add TODO to implement model
and backend-specific request parameters.

* gptel-gemini.el (gptel-make-gemini, gptel--request-data): Add
request-params keywod to `gptel-make-gemini'.  Merge model and
backend-specific request parameters when sending a request.

* gptel-curl.el (gptel-curl-get-response): Check model and
backend-specific stream settings in their request-params slot when
sending the request.  These take priority over the global
`gptel-stream' and the backend's `:stream' value.

* gptel-anthropic.el (gptel-make-anthropic, gptel--request-data):
Add request-params keywod to `gptel-make-ollama'.  Merge model and
backend-specific request parameters when sending a request.

gptel-anthropic.el

@@ -73,7 +73,11 @@
            :messages [,@prompts])))
     (when gptel-temperature
       (plist-put prompts-plist :temperature gptel-temperature))
-    prompts-plist))
+    ;; Merge request params with model and backend params.
+    (gptel--merge-plists
+     prompts-plist
+     (gptel-backend-request-params gptel-backend)
+     (gptel--model-request-params  gptel-model))))
 
 (cl-defmethod gptel--parse-buffer ((_backend gptel-anthropic) &optional max-entries)
   (let ((prompts) (prop)
@@ -262,6 +266,9 @@ Keys:
 
 - `:cutoff-date': the knowledge cutoff date.
 
+- `:request-params': a plist of additional request parameters to
+  include when using this model.
+
 Information about the Anthropic models was obtained from the following
 sources:
 
@@ -271,7 +278,7 @@ sources:
 
 ;;;###autoload
 (cl-defun gptel-make-anthropic
-    (name &key curl-args stream key
+    (name &key curl-args stream key request-params
           (header
            (lambda () (when-let (key (gptel--get-api-key))
                    `(("x-api-key" . ,key)
@@ -324,7 +331,12 @@ alist, like:
  ((\"Content-Type\" . \"application/json\"))
 
 KEY is a variable whose value is the API key, or function that
-returns the key."
+returns the key.
+
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for."
   (declare (indent 1))
   (let ((backend (gptel--make-anthropic
                   :curl-args curl-args
@@ -336,6 +348,7 @@ returns the key."
                   :protocol protocol
                   :endpoint endpoint
                   :stream stream
+                  :request-params request-params
                   :url (if protocol
                            (concat protocol "://" host endpoint)
                          (concat host endpoint)))))

gptel-curl.el

@@ -109,7 +109,16 @@ the response is inserted into the current buffer after point."
                              (random) (emacs-pid) (user-full-name)
                              (recent-keys))))
          (args (gptel-curl--get-args (plist-get info :data) token))
-         (stream (and gptel-stream (gptel-backend-stream gptel-backend)))
+         (stream (and ;; Check model-specific request-params for streaming preference
+                  (let* ((model-params (gptel--model-request-params gptel-model))
+                         (stream-spec (plist-get model-params :stream)))
+                    ;; If not present, there is no model-specific preference
+                    (or (not (memq :stream model-params))
+                        ;; If present, it must not be :json-false or nil
+                        (and stream-spec (not (eq stream-spec :json-false)))))
+                  ;; Check global and backend-specific streaming settings
+                  gptel-stream
+                  (gptel-backend-stream gptel-backend)))
          (backend (buffer-local-value 'gptel-backend (plist-get info :buffer)))
          (process (apply #'start-process "gptel-curl"
                          (generate-new-buffer "*gptel-curl*") "curl" args)))

gptel-gemini.el

@@ -88,7 +88,11 @@
     (when params
       (plist-put prompts-plist
                  :generationConfig params))
-    prompts-plist))
+    ;; Merge request params with model and backend params.
+    (gptel--merge-plists
+     prompts-plist
+     (gptel-backend-request-params gptel-backend)
+     (gptel--model-request-params  gptel-model))))
 
 (cl-defmethod gptel--parse-buffer ((_backend gptel-gemini) &optional max-entries)
   (let ((prompts) (prop)
@@ -230,6 +234,9 @@ Keys:
 
 - `:cutoff-date': the knowledge cutoff date.
 
+- `:request-params': a plist of additional request parameters to
+  include when using this model.
+
 Information about the Gemini models was obtained from the following
 source:
 
@@ -238,7 +245,8 @@ source:
 
 ;;;###autoload
 (cl-defun gptel-make-gemini
-    (name &key curl-args header key (stream nil)
+    (name &key curl-args header key request-params
+          (stream nil)
           (host "generativelanguage.googleapis.com")
           (protocol "https")
           (models gptel--gemini-models)
@@ -289,7 +297,12 @@ alist, like:
  ((\"Content-Type\" . \"application/json\"))
 
 KEY (optional) is a variable whose value is the API key, or
-function that returns the key."
+function that returns the key.
+
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for."
   (declare (indent 1))
   (let ((backend (gptel--make-gemini
                   :curl-args curl-args
@@ -300,6 +313,7 @@ function that returns the key."
                   :protocol protocol
                   :endpoint endpoint
                   :stream stream
+                  :request-params request-params
                   :key key
                   :url (lambda ()
                          (let ((method (if (and stream

gptel-kagi.el

@@ -69,6 +69,7 @@
                      (concat "\n\n" (mapconcat #'identity ref-strings "\n")))))
         (concat output references)))
 
+;; TODO: Add model and backend-specific request-params support
 (cl-defmethod gptel--request-data ((_backend gptel-kagi) prompts)
   "JSON encode PROMPTS for Kagi."
   (pcase-exhaustive (gptel--model-name gptel-model)

gptel-ollama.el

@@ -80,9 +80,7 @@ Intended for internal use only.")
            :messages [,@prompts]
            :stream ,(or (and gptel-stream gptel-use-curl
                          (gptel-backend-stream gptel-backend))
-                     :json-false)))
-        ;; TODO num_ctx chosen according to #330, make customizable
-        (options-plist (list :num_ctx 8192)))
+                     :json-false))))
     (when gptel-temperature
       (setq options-plist
             (plist-put options-plist :temperature
@@ -91,9 +89,11 @@ Intended for internal use only.")
       (setq options-plist
             (plist-put options-plist :num_predict
                        gptel-max-tokens)))
-    (when options-plist
-      (plist-put prompts-plist :options options-plist))
-    prompts-plist))
+    ;; Merge request params with model and backend params.
+    (gptel--merge-plists
+     prompts-plist
+     (gptel-backend-request-params gptel-backend)
+     (gptel--model-request-params  gptel-model))))
 
 (cl-defmethod gptel--parse-buffer ((_backend gptel-ollama) &optional max-entries)
   (let ((prompts) (prop)
@@ -177,7 +177,7 @@ If INJECT-MEDIA is non-nil wrap it with base64-encoded media files in the contex
 
 ;;;###autoload
 (cl-defun gptel-make-ollama
-    (name &key curl-args header key models stream
+    (name &key curl-args header key models stream request-params
           (host "localhost:11434")
           (protocol "http")
           (endpoint "/api/chat"))
@@ -227,13 +227,18 @@ KEY (optional) is a variable whose value is the API key, or
 function that returns the key.  This is typically not required
 for local models like Ollama.
 
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for.
+
 Example:
 -------
 
  (gptel-make-ollama
    \"Ollama\"
    :host \"localhost:11434\"
-   :models \\='(\"mistral:latest\")
+   :models \\='(mistral:latest)
    :stream t)"
   (declare (indent 1))
   (let ((backend (gptel--make-ollama
@@ -246,6 +251,7 @@ Example:
                   :protocol protocol
                   :endpoint endpoint
                   :stream stream
+                  :request-params request-params
                   :url (if protocol
                            (concat protocol "://" host endpoint)
                          (concat host endpoint)))))

gptel-openai.el

@@ -50,6 +50,7 @@
 (declare-function json-read "json")
 (declare-function gptel-prompt-prefix-string "gptel")
 (declare-function gptel-response-prefix-string "gptel")
+(declare-function gptel--merge-plists "gptel")
 (declare-function gptel-context--wrap "gptel-context")
 
 (defmacro gptel--json-read ()
@@ -104,7 +105,8 @@ with differing settings.")
     (gptel-backend (:constructor gptel--make-backend)
                    (:copier gptel--copy-backend))
   name host header protocol stream
-  endpoint key models url curl-args)
+  endpoint key models url request-params
+  curl-args)
 
 ;;; OpenAI (ChatGPT)
 (cl-defstruct (gptel-openai (:constructor gptel--make-openai)
@@ -140,8 +142,12 @@ with differing settings.")
     (when gptel-temperature
       (plist-put prompts-plist :temperature gptel-temperature))
     (when gptel-max-tokens
-      (plist-put prompts-plist :max_tokens gptel-max-tokens))
-    prompts-plist))
+      (plist-put prompts-plist :max_completion_tokens gptel-max-tokens))
+    ;; Merge request params with model and backend params.
+    (gptel--merge-plists
+     prompts-plist
+     (gptel-backend-request-params gptel-backend)
+     (gptel--model-request-params  gptel-model))))
 
 (cl-defmethod gptel--parse-buffer ((_backend gptel-openai) &optional max-entries)
   (let ((prompts) (prop)
@@ -248,7 +254,7 @@ files in the context."
 
 ;;;###autoload
 (cl-defun gptel-make-openai
-    (name &key curl-args models stream key
+    (name &key curl-args models stream key request-params
           (header
            (lambda () (when-let (key (gptel--get-api-key))
                    `(("Authorization" . ,(concat "Bearer " key))))))
@@ -298,7 +304,12 @@ alist, like:
  ((\"Content-Type\" . \"application/json\"))
 
 KEY (optional) is a variable whose value is the API key, or
-function that returns the key."
+function that returns the key.
+
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for."
   (declare (indent 1))
   (let ((backend (gptel--make-openai
                   :curl-args curl-args
@@ -310,6 +321,7 @@ function that returns the key."
                   :protocol protocol
                   :endpoint endpoint
                   :stream stream
+                  :request-params request-params
                   :url (if protocol
                            (concat protocol "://" host endpoint)
                          (concat host endpoint)))))
@@ -325,7 +337,7 @@ function that returns the key."
           (protocol "https")
           (header (lambda () `(("api-key" . ,(gptel--get-api-key)))))
           (key 'gptel-api-key)
-          models stream endpoint)
+          models stream endpoint request-params)
   "Register an Azure backend for gptel with NAME.
 
 Keyword arguments:
@@ -334,7 +346,7 @@ CURL-ARGS (optional) is a list of additional Curl arguments.
 
 HOST is the API host.
 
-MODELS is a list of available model names.
+MODELS is a list of available model names, as symbols.
 
 STREAM is a boolean to toggle streaming responses, defaults to
 false.
@@ -351,6 +363,11 @@ alist, like:
 KEY (optional) is a variable whose value is the API key, or
 function that returns the key.
 
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for.
+
 Example:
 -------
 
@@ -361,7 +378,7 @@ Example:
   :endpoint
   \"/openai/deployments/DEPLOYMENT_NAME/completions?api-version=2023-05-15\"
   :stream t
-  :models \\='(\"gpt-3.5-turbo\" \"gpt-4\"))"
+  :models \\='(gpt-3.5-turbo gpt-4))"
   (declare (indent 1))
   (let ((backend (gptel--make-openai
                   :curl-args curl-args
@@ -373,6 +390,7 @@ Example:
                   :protocol protocol
                   :endpoint endpoint
                   :stream stream
+                  :request-params request-params
                   :url (if protocol
                            (concat protocol "://" host endpoint)
                          (concat host endpoint)))))
@@ -392,7 +410,7 @@ CURL-ARGS (optional) is a list of additional Curl arguments.
 
 HOST is where GPT4All runs (with port), typically localhost:4891
 
-MODELS is a list of available model names.
+MODELS is a list of available model names, as symbols.
 
 STREAM is a boolean to toggle streaming responses, defaults to
 false.
@@ -411,14 +429,19 @@ KEY (optional) is a variable whose value is the API key, or
 function that returns the key. This is typically not required for
 local models like GPT4All.
 
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for.
+
 Example:
 -------
 
 (gptel-make-gpt4all
  \"GPT4All\"
  :protocol \"http\"
  :host \"localhost:4891\"
- :models \\='(\"mistral-7b-openorca.Q4_0.gguf\"))")
+ :models \\='(mistral-7b-openorca.Q4_0.gguf))")
 
 (provide 'gptel-openai)
 ;;; gptel-openai.el ends here

gptel-privategpt.el

@@ -96,12 +96,16 @@
       (plist-put prompts-plist :temperature gptel-temperature))
     (when gptel-max-tokens
       (plist-put prompts-plist :max_tokens gptel-max-tokens))
-    prompts-plist))
+    ;; Merge request params with model and backend params.
+    (gptel--merge-plists
+     prompts-plist
+     (gptel-backend-request-params gptel-backend)
+     (gptel--model-request-params  gptel-model))))
 
 
 ;;;###autoload
 (cl-defun gptel-make-privategpt
-    (name &key curl-args stream key
+    (name &key curl-args stream key request-params
           (header
            (lambda () (when-let (key (gptel--get-api-key))
 			`(("Authorization" . ,(concat "Bearer " key))))))
@@ -137,7 +141,12 @@ KEY is a variable whose value is the API key, or function that
 returns the key.
 
 CONTEXT and SOURCES: if true (the default), use available context
-and provide sources used by the model to generate the response."
+and provide sources used by the model to generate the response.
+
+REQUEST-PARAMS (optional) is a plist of additional HTTP request
+parameters (as plist keys) and values supported by the API.  Use
+these to set parameters that gptel does not provide user options
+for."
   (declare (indent 1))
   (let ((backend (gptel--make-privategpt
                   :curl-args curl-args
@@ -149,6 +158,7 @@ and provide sources used by the model to generate the response."
                   :protocol protocol
                   :endpoint endpoint
                   :stream stream
+                  :request-params request-params
                   :url (if protocol
                            (concat protocol "://" host endpoint)
                          (concat host endpoint))