Command empty strings (#839)

* Added ctx object to all system struct's constructors

The idea behind this commit is to set the stage for adding aditional
logging metadata.

* Changed: Improved logging

* Added new flags `--log-level` and `-l` to be consistent with other goss
flags.
  * `--loglevel` and `-L` will be deprecated in a future release
* Log level accepts any casing, so DEBUG and debug are both valid cli opts
* Add log level support for `add` and `autoadd` commands

* Changed: Goss add command default to empty string

Changed the behavior of `goss add` on a command, if the value of stdout or stderr is
empty, it will be defaulted to an empty string instead of an empty
array. The behavior remains unchanged when there is output; the value
will be an array.

This approach provides the following benefits:
* Tests will fail if an empty string receives a value.
* Arrays allows for simpler deletion of lines that are not relevant
to the test assertion.

closes #820

* fix build error

integration-tests/goss/alpine3/goss-expected-q.yaml

@@ -13,10 +13,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -49,13 +49,13 @@ group:
 command:
   echo 'hi':
     exit-status: 0
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
 dns:
   CAA:dnstest.io:

integration-tests/goss/alpine3/goss-expected.yaml

@@ -19,10 +19,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -62,11 +62,11 @@ command:
     exit-status: 0
     stdout:
     - hi
-    stderr: []
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
+    stdout: ""
     stderr:
     - 'sh: foobar: not found'
     timeout: 10000

integration-tests/goss/centos7/goss-expected-q.yaml

@@ -13,10 +13,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -49,13 +49,13 @@ group:
 command:
   echo 'hi':
     exit-status: 0
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
 dns:
   CAA:dnstest.io:

integration-tests/goss/centos7/goss-expected.yaml

@@ -19,10 +19,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -68,11 +68,11 @@ command:
     exit-status: 0
     stdout:
     - hi
-    stderr: []
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
+    stdout: ""
     stderr:
     - 'sh: foobar: command not found'
     timeout: 10000

integration-tests/goss/generate_goss.sh

@@ -22,7 +22,7 @@ done
 [[ $OS == "centos7" ]] && user="apache" || user="www-data"
 goss a "${args[@]}" package $package foobar vim-tiny
 
-goss a "${args[@]}" addr --timeout 1s google.com:443 google.com:22
+goss a "${args[@]}" addr --timeout 1s httpbin:80 httpbin:22
 
 goss a "${args[@]}" addr --timeout 1s udp://8.8.8.8:53
 

integration-tests/goss/goss-shared.yaml

@@ -70,13 +70,13 @@ service:
     runlevels: {{toJson $runlevels}}
 {{end}}
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 5000
-  tcp://google.com:80:
+  tcp://httpbin:999:
     reachable: false
     timeout: 5000
     local-address: 127.0.0.1

integration-tests/goss/trusty/goss-expected-q.yaml

@@ -13,10 +13,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -49,13 +49,13 @@ group:
 command:
   echo 'hi':
     exit-status: 0
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
 dns:
   CAA:dnstest.io:

integration-tests/goss/trusty/goss-expected.yaml

@@ -19,10 +19,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -68,11 +68,11 @@ command:
     exit-status: 0
     stdout:
     - hi
-    stderr: []
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
+    stdout: ""
     stderr:
     - 'sh: 1: foobar: not found'
     timeout: 10000

integration-tests/goss/wheezy/goss-expected-q.yaml

@@ -13,10 +13,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -49,13 +49,13 @@ group:
 command:
   echo 'hi':
     exit-status: 0
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
-    stderr: []
+    stdout: ""
+    stderr: ""
     timeout: 10000
 dns:
   CAA:dnstest.io:

integration-tests/goss/wheezy/goss-expected.yaml

@@ -19,10 +19,10 @@ package:
   vim-tiny:
     installed: false
 addr:
-  tcp://google.com:22:
+  tcp://httpbin:22:
     reachable: false
     timeout: 1000
-  tcp://google.com:443:
+  tcp://httpbin:80:
     reachable: true
     timeout: 1000
   udp://8.8.8.8:53:
@@ -68,11 +68,11 @@ command:
     exit-status: 0
     stdout:
     - hi
-    stderr: []
+    stderr: ""
     timeout: 10000
   foobar:
     exit-status: 127
-    stdout: []
+    stdout: ""
     stderr:
     - 'sh: 1: foobar: not found'
     timeout: 10000

resource/command.go

@@ -76,18 +76,24 @@ func NewCommand(sysCommand system.Command, config util.Config) (*Command, error)
 	c := &Command{
 		id:         command,
 		ExitStatus: exitStatus,
-		Stdout:     []string{},
-		Stderr:     []string{},
+		Stdout:     "",
+		Stderr:     "",
 		Timeout:    config.TimeOutMilliSeconds(),
 	}
 
 	if !contains(config.IgnoreList, "stdout") {
 		stdout, _ := sysCommand.Stdout()
-		c.Stdout = readerToSlice(stdout)
+		outSlice := readerToSlice(stdout)
+		if len(outSlice) != 0 {
+			c.Stdout = outSlice
+		}
 	}
 	if !contains(config.IgnoreList, "stderr") {
 		stderr, _ := sysCommand.Stderr()
-		c.Stderr = readerToSlice(stderr)
+		errSlice := readerToSlice(stderr)
+		if len(errSlice) != 0 {
+			c.Stderr = errSlice
+		}
 	}
 
 	return c, err