New ComX specifying error output string (closes #342)

4 files changed, 33 insertions, 19 deletions

diff --git a/changelog.md b/changelog.md
index 20aecd4..0c2dc51 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,9 @@
+## Version 0.28
+
+_New features_
+
+  - New `ComX`, which runs a command with custom exit error message.
+
 ## Version 0.27 (July, 2018)
 
 _New features_
diff --git a/readme.md b/readme.md
index 92727bb..2022adf 100644
--- a/readme.md
+++ b/readme.md
@@ -1284,7 +1284,20 @@ _uname_ only once), while
 
         Run Com "date" ["+\"%a %b %_d %H:%M\""] "mydate" 600
 
-can be used in the output template as `%mydate%`
+can be used in the output template as `%mydate%`.
+
+Sometimes, you don't mind if the command executed exits with an error,
+or you might want to display a custom message in that case.  To that
+end, you can use the `ComX` variant:
+
+`ComX ProgramName Args ExitMessage Alias RefreshRate`
+
+Works like `Com`, but displaying `ExitMessage` (a string) if the
+execution fails.  For instance:
+
+        Run ComX "date" ["+\"%a %b %_d %H:%M\""] "N/A" "mydate" 600
+
+will display "N/A" if for some reason the `date` invocation fails.
 
 ## Other Plugins
 
diff --git a/src/Commands.hs b/src/Commands.hs
index e4402fc..5b11ca3 100644
--- a/src/Commands.hs
+++ b/src/Commands.hs
@@ -48,6 +48,7 @@ class Show e => Exec e where
     trigger _ sh  = sh Nothing
 
 data Command = Com Program Args Alias Rate
+             | ComX Program Args String Alias Rate
                deriving (Show,Read,Eq)
 
 type Args    = [String]
@@ -56,10 +57,12 @@ type Alias   = String
 type Rate    = Int
 
 instance Exec Command where
-    alias (Com p    _    a _)
-        | p /= ""             = if a == "" then p else a
-        | otherwise           = ""
-    start (Com prog args _ r) cb = if r > 0 then go else exec
+    alias (ComX p _ _ a _) =
+      if p /= "" then (if a == "" then p else a) else ""
+    alias (Com p a al r) = alias (ComX p a "" al r)
+    start (Com p as al r) cb =
+      start (ComX p as ("Could not execute command " ++ p) al r) cb
+    start (ComX prog args msg _ r) cb = if r > 0 then go else exec
         where go = exec >> tenthSeconds r >> go
               exec = do
                 (i,o,e,p) <- runInteractiveProcess prog args Nothing Nothing
@@ -71,8 +74,7 @@ instance Exec Command where
                   ExitSuccess -> do str <- getL
                                     closeHandles
                                     cb str
-                  _ -> do closeHandles
-                          cb $ "Could not execute command " ++ prog
+                  _ -> closeHandles >> cb msg
 
 
 -- | Work around to the Int max bound: since threadDelay takes an Int, it
diff --git a/stack.yaml b/stack.yaml
index 80ea090..a46d035 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,14 +1,7 @@
-resolver: lts-10.3
-allow-newer: true
+resolver: lts-12.1
 packages:
 - .
-# Dependency packages to be pulled from upstream that are not in the resolver
-# (e.g., acme-missiles-0.3)
-extra-deps: [iwlib-0.1.0]
-
-# Override default flag values for local packages and extra-deps
-# flags: {}
-
-# Control whether we use the GHC we find on the path
-# system-ghc: true
-
+extra-deps:
+- iwlib-0.1.0
+- parsec-numbers-0.1.0
+- alsa-mixer-0.2.0.3