Give a more helpful message on elm install

builder/src/Elm/Install.hs

@@ -26,6 +26,7 @@ import qualified Elm.Project.Root as Root
 import Reporting.Doc ((<>), (<+>))
 import qualified Reporting.Doc as D
 import qualified Reporting.Exit as Exit
+import qualified Reporting.Exit.Install as E
 import qualified Reporting.Task as Task
 
 
@@ -148,7 +149,7 @@ addToApp pkg info@(Project.AppInfo _ _ deps tests trans) =
 
           Nothing ->
             do  badNames <- filterM isBadElm (pkg : Map.keys old)
-                lift $ Task.throw (Exit.NoSolution badNames)
+                lift $ Task.throw (Exit.Install (E.NoSolution badNames))
 
 
 addToAppHelp :: Name -> Project.AppInfo -> Solver.Solver (Map Name Version)
@@ -189,7 +190,7 @@ addToPkg pkg info@(Project.PkgInfo _ _ _ _ _ deps tests _) =
           Nothing ->
             do  let pkgs = Map.keys deps ++ Map.keys tests
                 badNames <- filterM isBadElm (pkg : pkgs)
-                lift $ Task.throw (Exit.NoSolution badNames)
+                lift $ Task.throw (Exit.Install (E.NoSolution badNames))
 
 
 addToPkgHelp :: Name -> Project.PkgInfo -> Solver.Solver (Map Name Constraint)

builder/src/Reporting/Exit.hs

@@ -8,9 +8,7 @@ module Reporting.Exit
   where
 
 
-import qualified Elm.Compiler as Compiler
 import qualified Elm.Compiler.Module as Module
-import qualified Elm.Package as Pkg
 import qualified Json.Encode as Encode
 import qualified Reporting.Doc as D
 import qualified Reporting.Exit.Assets as Asset
@@ -22,6 +20,7 @@ import qualified Reporting.Exit.Diff as Diff
 import qualified Reporting.Exit.Help as Help
 import qualified Reporting.Exit.Http as Http
 import qualified Reporting.Exit.Make as Make
+import qualified Reporting.Exit.Install as Install
 import qualified Reporting.Exit.Publish as Publish
 
 
@@ -39,12 +38,10 @@ data Exit
   | Deps Deps.Exit
   | Diff Diff.Exit
   | Make Make.Exit
+  | Install Install.Exit
   | Publish Publish.Exit
   | BadHttp String Http.Exit
 
-  -- misc
-  | NoSolution [Pkg.Name]
-
 
 
 -- RENDERERS
@@ -116,38 +113,11 @@ toReport exit =
     Make makeExit ->
       Make.toReport makeExit
 
+    Install installExit ->
+      Install.toReport installExit
+
     Publish publishExit ->
       Publish.toReport publishExit
 
     BadHttp url httpExit ->
       Http.toReport url httpExit
-
-    NoSolution badPackages ->
-      case badPackages of
-        [] ->
-          Help.report "UNSOLVABLE DEPENDENCIES" (Just "elm.json")
-            "This usually happens if you try to modify dependency constraints by\
-            \ hand. I recommend deleting any dependency you added recently (or all\
-            \ of them if things are bad) and then adding them again with:"
-            [ D.indent 4 $ D.green "elm install"
-            , D.reflow $
-                "And do not be afaid to ask for help on Slack if you get stuck!"
-            ]
-
-        _:_ ->
-          Help.report "OLD DEPENDENCIES" (Just "elm.json")
-            ( "The following packages do not work with Elm " ++ Pkg.versionToString Compiler.version ++ " right now:"
-            )
-            [ D.indent 4 $ D.vcat $ map (D.red . D.fromString . Pkg.toString) badPackages
-            , D.reflow $
-                "This may be because it is not upgraded yet. It may be because a\
-                \ better solution came along, so there was no need to upgrade it.\
-                \ Etc. Try asking around on Slack to learn more about the topic."
-            , D.toSimpleNote
-                "Whatever the case, please be kind to the relevant package authors! Having\
-                \ friendly interactions with users is great motivation, and conversely, getting\
-                \ berated by strangers on the internet sucks your soul dry. Furthermore, package\
-                \ authors are humans with families, friends, jobs, vacations, responsibilities,\
-                \ goals, etc. They face obstacles outside of their technical work you will never\
-                \ know about, so please assume the best and try to be patient and supportive!"
-            ]

builder/src/Reporting/Exit/Install.hs

@@ -0,0 +1,82 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Reporting.Exit.Install
+  ( Exit(..)
+  , toReport
+  )
+  where
+
+
+import qualified Elm.Compiler as Compiler
+import qualified Elm.Package as Pkg
+import qualified Reporting.Doc as D
+import qualified Reporting.Exit.Help as Help
+
+
+
+-- EXITS
+
+
+data Exit
+  = NoArgs FilePath
+  | NoSolution [Pkg.Name]
+
+
+
+-- TO REPORT
+
+
+toReport :: Exit -> Help.Report
+toReport exit =
+  case exit of
+    NoArgs cacheDir ->
+      Help.report "INSTALL WHAT?" Nothing
+        "I am expecting commands like:"
+        [ D.green $ D.indent 4 $ D.vcat $
+            [ "elm install elm-lang/http"
+            , "elm install elm-lang/json"
+            , "elm install elm-lang/random"
+            ]
+        , D.toFancyHint
+            ["In","JavaScript","folks","run","`npm install`","to","start","projects."
+            ,"\"Gotta","download","everything!\"","But","why","download","packages"
+            ,"again","and","again?","Instead,","Elm","caches","packages","in"
+            ,D.dullyellow (D.fromString cacheDir)
+            ,"so","each","one","is","downloaded","and","built","ONCE","on","your","machine."
+            ,"Elm","projects","check","that","cache","before","trying","the","internet."
+            ,"This","reduces","build","times,","reduces","server","costs,","and","makes","it"
+            ,"easier","to","work","offline.","As","a","result"
+            ,D.dullcyan "elm install","is","only","for","adding","dependencies","to","elm.json,"
+            ,"whereas",D.dullcyan "elm make","is","in","charge","of","gathering","dependencies"
+            ,"and","building","everything.","So","maybe","try",D.green "elm make","instead?"
+            ]
+        ]
+
+    NoSolution badPackages ->
+      case badPackages of
+        [] ->
+          Help.report "UNSOLVABLE DEPENDENCIES" (Just "elm.json")
+            "This usually happens if you try to modify dependency constraints by\
+            \ hand. I recommend deleting any dependency you added recently (or all\
+            \ of them if things are bad) and then adding them again with:"
+            [ D.indent 4 $ D.green "elm install"
+            , D.reflow $
+                "And do not be afaid to ask for help on Slack if you get stuck!"
+            ]
+
+        _:_ ->
+          Help.report "OLD DEPENDENCIES" (Just "elm.json")
+            ( "The following packages do not work with Elm " ++ Pkg.versionToString Compiler.version ++ " right now:"
+            )
+            [ D.indent 4 $ D.vcat $ map (D.red . D.fromString . Pkg.toString) badPackages
+            , D.reflow $
+                "This may be because it is not upgraded yet. It may be because a\
+                \ better solution came along, so there was no need to upgrade it.\
+                \ Etc. Try asking around on Slack to learn more about the topic."
+            , D.toSimpleNote
+                "Whatever the case, please be kind to the relevant package authors! Having\
+                \ friendly interactions with users is great motivation, and conversely, getting\
+                \ berated by strangers on the internet sucks your soul dry. Furthermore, package\
+                \ authors are humans with families, friends, jobs, vacations, responsibilities,\
+                \ goals, etc. They face obstacles outside of their technical work you will never\
+                \ know about, so please assume the best and try to be patient and supportive!"
+            ]

elm.cabal

@@ -118,6 +118,7 @@ Executable elm
         Reporting.Exit.Help,
         Reporting.Exit.Http,
         Reporting.Exit.Make,
+        Reporting.Exit.Install,
         Reporting.Exit.Publish,
         Reporting.Progress,
         Reporting.Progress.Bar,

ui/terminal/src/Install.hs

@@ -1,8 +1,14 @@
-module Install (run) where
+module Install
+  ( Args(..)
+  , run
+  )
+  where
 
 
 import qualified Elm.Install as Install
 import qualified Elm.Package as Pkg
+import qualified Reporting.Exit as Exit
+import qualified Reporting.Exit.Install as E
 import qualified Reporting.Task as Task
 import qualified Reporting.Progress.Terminal as Terminal
 
@@ -11,7 +17,19 @@ import qualified Reporting.Progress.Terminal as Terminal
 -- RUN
 
 
-run :: Pkg.Name -> () -> IO ()
-run pkg () =
+data Args
+  = NoArgs
+  | Install Pkg.Name
+
+
+run :: Args -> () -> IO ()
+run args () =
   do  reporter <- Terminal.create
-      Task.run reporter $ Install.install pkg
+      Task.run reporter $
+        case args of
+          NoArgs ->
+            do  cacheDir <- Task.getPackageCacheDir
+                Task.throw (Exit.Install (E.NoArgs cacheDir))
+
+          Install pkg ->
+            Install.install pkg

ui/terminal/src/Main.hs

@@ -213,8 +213,14 @@ install =
             "What if two projects use different versions of the same package? No problem!\
             \ Each project is independent, so there cannot be conflics like that!"
         ]
+
+    installArgs =
+      oneOf
+        [ require0 Install.NoArgs
+        , require1 Install.Install package
+        ]
   in
-  Interface "install" (Common summary) details example (required package) noFlags Install.run
+  Interface "install" (Common summary) details example installArgs noFlags Install.run