add lint that (let [] ...) should be (do ...)

src/fennel-ls/config.fnl

@@ -35,7 +35,8 @@ There are no global settings. They're all stored in the `server` object.
            :var-never-set (option true)
            :op-with-no-arguments (option true)
            :multival-in-middle-of-call (option true)
-           :no-decreasing-comparison (option false)}
+           :no-decreasing-comparison (option false)
+           :empty-let (option true)}
    :libraries (option {})
    :extra-globals (option "")})
 

src/fennel-ls/lint.fnl

@@ -242,6 +242,22 @@ the `file.diagnostics` field, filling it with diagnostics."
      :severity message.severity.WARN
      :code :inline-unpack}))
 
+(λ empty-let [server file _ call]
+  (case call
+    (where [let* binding]
+           (. file.lexical call)
+           (sym? let* :let)
+           (fennel.sequence? binding)
+           (= 0 (length binding)))
+    (diagnostic {:range (message.ast->range server file binding)
+                 :message "use do instead of let with no bindings"
+                 :severity message.severity.WARN
+                 :code :empty-let}
+                #[(let [{: start} (message.ast->range server file let*)
+                        {: end} (message.ast->range server file binding)]
+                    {:range {: start : end}
+                     :newText "do"})])))
+
 (λ add-lint-diagnostics [server file]
   "fill up the file.diagnostics table with linting things"
   (let [lints server.configuration.lints
@@ -272,6 +288,8 @@ the `file.diagnostics` field, filling it with diagnostics."
           (table.insert diagnostics (op-with-no-arguments server file head call)))
         (when lints.no-decreasing-comparison
           (table.insert diagnostics (no-decreasing-comparison server file head call)))
+        (when lints.empty-let
+          (table.insert diagnostics (empty-let server file head call)))
 
         ;; argument lints
         ;; every argument to a special or a function call

test/cli.fnl

@@ -9,10 +9,11 @@
       (: :close))
     (let [output-file (io.popen (.. "./fennel-ls --lint "
                                     input-file-name)
-                                :r)]
+                                :r)
+          contents (output-file:read :*a)]
+      (os.remove input-file-name)
       (faith.= (.. input-file-name ":1:7: warning: unused definition: x\n")
-               (output-file:read :*a))
+               contents))
-      (os.remove input-file-name))
     nil))
 
 {: test-lint}

test/lint.fnl

@@ -7,18 +7,19 @@
    (accumulate [result nil
                 i d (ipairs diagnostics)
                 &until result]
-     (if (and (or (= e.message nil)
+     (let [d (or d.self d)]
-                  (if (= (type e.message) "function")
+       (if (and (or (= e.message nil)
-                    (e.message d.message)
+                    (if (= (type e.message) "function")
-                    (= e.message d.message)))
+                      (e.message d.message)
-              (or (= e.code nil)
+                      (= e.message d.message)))
-                  (= e.code d.code))
+                (or (= e.code nil)
-              (or (= e.range nil)
+                    (= e.code d.code))
-                  (and (= e.range.start.line      d.range.start.line)
+                (or (= e.range nil)
-                       (= e.range.start.character d.range.start.character)
+                    (and (= e.range.start.line      d.range.start.line)
-                       (= e.range.end.line        d.range.end.line)
+                         (= e.range.start.character d.range.start.character)
-                       (= e.range.end.character   d.range.end.character))))
+                         (= e.range.end.line        d.range.end.line)
-       i)))
+                         (= e.range.end.character   d.range.end.character))))
+         i))))
 
 (fn check [file-contents expected ?unexpected]
   (let [{: diagnostics} (create-client file-contents)]
@@ -32,8 +33,8 @@
       (let [i (find diagnostics e)]
         (faith.is i (.. "No lint matching " (view e) "\n"
                         "from:    " (view file-contents) "\n"
-                        (view diagnostics {:empty-as-sequence? true
+                        "possible matches: " (view diagnostics {:empty-as-sequence? true
-                                           :escape-newlines? true})))
+                                                                :escape-newlines? true})))
         (table.remove diagnostics i)))))
 
 (fn assert-ok [file-contents]
@@ -257,12 +258,21 @@
   (assert-ok "(and false 1)")
   (assert-ok "(and nil 1)")
   (check "(and)"
-         {:message "write true instead of (and)"
+         [{:message "write true instead of (and)"
-          :code :op-with-no-arguments
+           :code :op-with-no-arguments
-          :range {:start {:characer 0 :line 0}
+           :range {:start {:character 0 :line 0}
-                  :end {:character 5 :line 0}}})
+                   :end {:character 5 :line 0}}}])
   nil)
 
+(fn test-empty-let []
+  (assert-ok "(let [x 1] x)")
+  (check "(let [] print)"
+         [{:message "use do instead of let with no bindings"
+           :code :empty-let
+           :range {:start {:character 5 :line 0}
+                   :end {:character 7 :line 0}}}])
+  (assert-ok "(-> [] (let print))"))
+
 ;; TODO lints:
 ;; duplicate keys in kv table
 ;; (tset <sym> <any>) --> (set (. <sym> <any>)) (might be wanted for compat?)
@@ -286,4 +296,5 @@
  : test-match-should-case
  : test-unpack-into-op
  : test-unpack-in-middle
- : test-op-with-no-arguments}
+ : test-op-with-no-arguments
+ : test-empty-let}

test/utils/client.fnl

@@ -30,6 +30,11 @@
      {: position
       :textDocument {:uri file}})))
 
+(fn completion-item-resolve [self completion-item]
+  (dispatch.handle* self.server
+    (message.create-request (next-id! self) :completionItem/resolve
+     completion-item)))
+
 (fn definition [self file position]
   (dispatch.handle* self.server
     (message.create-request (next-id! self) :textDocument/definition
@@ -87,6 +92,7 @@
   {:__index {: open-file!
              : pretend-this-file-exists!
              : completion
+             : completion-item-resolve
              : definition
              : hover
              : references