[#20] Add 'isSuccessful' predicate (#22)

Resolves #20

.github/workflows/ci.yml

@@ -18,11 +18,11 @@ jobs:
           - "8.2.2"
           - "8.4.4"
           - "8.6.5"
-          - "8.8.3"
-          - "8.10.1"
+          - "8.8.4"
+          - "8.10.2"
         exclude:
           - os: macOS-latest
-            ghc: 8.8.3
+            ghc: 8.8.4
           - os: macOS-latest
             ghc: 8.6.5
           - os: macOS-latest
@@ -62,7 +62,7 @@ jobs:
     strategy:
       matrix:
         stack: ["2.1.3"]
-        ghc: ["8.8.3"]
+        ghc: ["8.10.2"]
 
     steps:
     - uses: actions/checkout@v2

CHANGELOG.md

@@ -3,6 +3,12 @@
 `shellmet` uses [PVP Versioning][1].
 The changelog is available [on GitHub][2].
 
+## Unreleased
+
+* [#20](https://github.com/kowainik/shellmet/issues/20):
+  Add `isSuccess` function to show if the command succeded.
+* Upgrade GHC from `8.8.3` to `8.8.4`, `8.10.1` to `8.10.2`.
+
 ## 0.0.3.1 — May 7, 2020
 
 * [#18](https://github.com/kowainik/shellmet/issues/18):

shellmet.cabal

@@ -17,8 +17,8 @@ extra-doc-files:     README.md
 tested-with:         GHC == 8.2.2
                      GHC == 8.4.4
                      GHC == 8.6.5
-                     GHC == 8.8.3
-                     GHC == 8.10.1
+                     GHC == 8.8.4
+                     GHC == 8.10.2
 
 source-repository head
   type:                git

src/Shellmet.hs

@@ -20,6 +20,7 @@ module Shellmet
     ( ($|)
     , ($^)
     , ($?)
+    , isSuccess
     ) where
 
 import Control.Exception (catch)
@@ -80,3 +81,13 @@ infixl 4 $?
 ($?) :: IO a -> IO a -> IO a
 action $? handler = action `catch` \(_ :: IOError) -> handler
 {-# INLINE ($?) #-}
+
+{- | Returns the indicator of if the command succeded or not.
+
+>>> isSuccess $ "echo" ["Hello world!"]
+⚙  echo 'Hello world!'
+Hello world!
+True
+-}
+isSuccess :: IO a -> IO Bool
+isSuccess action = (True <$ action) $? pure False

stack.yaml

@@ -1 +1 @@
-resolver: lts-15.11
+resolver: nightly-2020-08-30