[Fix #1832] Add eldoc info for datomic query input parameters

CHANGELOG.md

@@ -17,6 +17,7 @@
 * [#1731](https://github.com/clojure-emacs/cider/issues/1731): Change code in order to use the new `cider.tasks/add-middleware` boot tasks.
 * [#1943](https://github.com/clojure-emacs/cider/pull/1943): Add interactive function to flush Compliment caches.
 * [#1726](https://github.com/clojure-emacs/cider/issues/1726): Order keys in printed nrepl message objects.
+* [#1832](https://github.com/clojure-emacs/cider/issues/1832): Add new customization variable `cider-eldoc-display-context-dependent-info` to control showing eldoc info for datomic query input parameters.
 
 ### Changes
 

cider-client.el

@@ -942,6 +942,16 @@ CONTEXT represents a completion context for compliment."
         nil
       eldoc)))
 
+(defun cider-sync-request:eldoc-datomic-query (symbol)
+  "Send \"eldoc-datomic-query\" op with parameter SYMBOL."
+  (when-let ((eldoc (thread-first `("op" "eldoc-datomic-query"
+                                    "ns" ,(cider-current-ns)
+                                    ,@(when symbol `("symbol" ,symbol)))
+                      (cider-nrepl-send-sync-request nil 'abort-on-input))))
+    (if (member "no-eldoc" (nrepl-dict-get eldoc "status"))
+        nil
+      eldoc)))
+
 (defun cider-sync-request:ns-list ()
   "Get a list of the available namespaces."
   (thread-first `("op" "ns-list"

cider-eldoc.el

@@ -86,6 +86,15 @@ displayed.  When nil, always display eldoc for first symbol of the sexp."
   :group 'cider
   :package-version '(cider . "0.13.0"))
 
+(defcustom cider-eldoc-display-context-dependent-info nil
+  "When non-nil, display context dependent info in the eldoc where possible.
+CIDER will try to add expected function arguments based on the current context,
+for example for the datomic.api/q function where it will show the expected
+inputs of the query at point."
+  :type 'boolean
+  :group 'cider
+  :package-version '(cider . "0.15.0"))
+
 (defun cider--eldoc-format-class-names (class-names)
   "Return a formatted CLASS-NAMES prefix string.
 CLASS-NAMES is a list of classes to which a Java interop form belongs.
@@ -398,10 +407,23 @@ This includes the arglist and ns and symbol name (if available)."
                                         "arglists" arglists
                                         "docstring" docstring
                                         "type" type)))
-                ;; middleware eldoc lookups are expensive, so we
-                ;; cache the last lookup.  This eliminates the need
-                ;; for extra middleware requests within the same sexp.
-                (setq cider-eldoc-last-symbol (list thing eldoc-plist))
+                ;; add context dependent args if requested by defcustom
+                ;; do not cache this eldoc info to avoid showing info
+                ;: of the previous context
+                (if cider-eldoc-display-context-dependent-info
+                    (cond
+                     ;; add inputs of datomic query
+                     ((and (equal ns-or-class "datomic.api")
+                           (equal name-or-member "q"))
+                      (let ((arglists (lax-plist-get eldoc-plist "arglists")))
+                        (lax-plist-put eldoc-plist "arglists"
+                                       (cider--eldoc-add-datomic-query-inputs-to-arglists arglists))))
+                     ;; if none of the clauses is successful, do cache the eldoc
+                     (t (setq cider-eldoc-last-symbol (list thing eldoc-plist))))
+                  ;; middleware eldoc lookups are expensive, so we
+                  ;; cache the last lookup.  This eliminates the need
+                  ;; for extra middleware requests within the same sexp.
+                  (setq cider-eldoc-last-symbol (list thing eldoc-plist)))
                 eldoc-plist))))))))
 
 (defun cider--eldoc-remove-dot (sym)
@@ -413,6 +435,24 @@ Only useful for interop forms.  Clojure forms would be returned unchanged."
   "Check whether FILE-NAME is representing an EDN file."
   (and file-name (equal (file-name-extension file-name) "edn")))
 
+(defun cider--eldoc-add-datomic-query-inputs-to-arglists (arglists)
+  "Add the expected inputs of the datomic query to the ARGLISTS."
+  (if (cider-second-sexp-in-list)
+    (let* ((query (cider-second-sexp-in-list))
+           (query-inputs (nrepl-dict-get
+                          (cider-sync-request:eldoc-datomic-query query)
+                          "inputs")))
+      (if query-inputs
+          (thread-first
+              (thread-last arglists
+                (car)
+                (remove "&")
+                (remove "inputs"))
+            (append (car query-inputs))
+            (list))
+        arglists))
+    arglists))
+
 (defun cider-eldoc ()
   "Backend function for eldoc to show argument list in the echo area."
   (when (and (cider-connected-p)

cider-util.el

@@ -165,6 +165,15 @@ Can only error if SKIP is non-nil."
       (forward-sexp 1)
       (cider-start-of-next-sexp))))
 
+(defun cider-second-sexp-in-list ()
+  "Return the second sexp in the list at point."
+  (condition-case nil
+      (save-excursion
+        (backward-up-list)
+        (forward-char)
+        (forward-sexp 2)
+        (cider-sexp-at-point))
+    (error nil)))
 
 ;;; Text properties
 

doc/configuration.md

@@ -165,6 +165,15 @@ its behaviour.
 | `nil`  | Messages are always truncated to fit in a single line of display in the echo area.  |
 | `truncate-sym-name-if-fit` or anything non-nil | Symbol name may be truncated if it will enable the function arglist or documentation string to fit on a single line. Otherwise, behavior is just like `t` case. |
 
+* CIDER will try to add expected function arguments based on the current context
+(for example for the `datomic.api/q` function where it will show the expected
+inputs of the query at point), if the variable `cider-eldoc-display-context-dependent-info`
+is non-nil:
+
+```el
+(setq cider-eldoc-display-context-dependent-info t)
+```
+
 ## Overlays
 
 When you evaluate code in Clojure files, the result is displayed in the buffer

test/cider-eldoc-tests.el

@@ -300,3 +300,11 @@
         (it "returns tries to display the var with the first line"
           (expect (cider-eldoc-format-sym-doc "kubaru.core/plane" "kubaru.core" "Line 1.\nLine 2.\nLine 3.")
                   :to-equal "kubaru.core/plane: Line 1."))))))
+
+(describe "cider--eldoc-add-datomic-query-inputs-to-arglists"
+  (it "adds the datomic query inputs of the query at point to the arglist"
+    (spy-on 'cider-second-sexp-in-list :and-return-value t)
+    (spy-on 'cider-sync-request:eldoc-datomic-query
+              :and-return-value '(dict "inputs" (("$" "?first-name"))))
+    (expect (cider--eldoc-add-datomic-query-inputs-to-arglists '(("query" "&" "inputs")))
+            :to-equal '(("query" "$" "?first-name")))))

test/cider-util-tests.el

@@ -183,3 +183,11 @@
   (it "returns the refcard correct url for snapshot cider versions"
     (setq cider-version "0.11.0-snapshot")
     (expect (cider-refcard-url) :to-equal "https://github.com/clojure-emacs/cider/raw/master/doc/cider-refcard.pdf")))
+
+(describe "cider-second-sexp-in-list"
+  (it "returns the second sexp in the list"
+    (with-temp-buffer
+      (clojure-mode)
+      (insert "(test-function arg1 arg2 arg3)")
+      (backward-char 2)
+      (expect (cider-second-sexp-in-list) :to-equal "arg1"))))