Merge pull request #681 from urfave/check-run-error-in-readme

Update README examples to check for errors

README.md

@@ -141,13 +141,17 @@ discovery. So a cli app can be as little as one line of code in `main()`.
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
 )
 
 func main() {
-  cli.NewApp().Run(os.Args)
+  err := cli.NewApp().Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -162,6 +166,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -176,7 +181,10 @@ func main() {
     return nil
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -200,6 +208,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -214,7 +223,10 @@ func main() {
     return nil
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -263,6 +275,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -276,7 +289,10 @@ func main() {
     return nil
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -292,6 +308,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -321,7 +338,10 @@ func main() {
     return nil
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -335,6 +355,7 @@ scanned.
 package main
 
 import (
+  "log"
   "os"
   "fmt"
 
@@ -368,7 +389,10 @@ func main() {
     return nil
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -389,6 +413,7 @@ For example this:
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -404,7 +429,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -430,6 +458,7 @@ list for the `Name`. e.g.
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -446,7 +475,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -470,6 +502,7 @@ For example this:
 package main
 
 import (
+  "log"
   "os"
   "sort"
 
@@ -513,7 +546,10 @@ func main() {
   sort.Sort(cli.FlagsByName(app.Flags))
   sort.Sort(cli.CommandsByName(app.Commands))
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -536,6 +572,7 @@ You can also have the default value set from the environment via `EnvVar`.  e.g.
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -553,7 +590,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -568,6 +608,7 @@ environment variable that resolves is used as the default.
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -585,7 +626,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -601,6 +645,7 @@ You can also have the default value set from file via `FilePath`.  e.g.
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -617,7 +662,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -668,6 +716,7 @@ package notmain
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -690,7 +739,10 @@ func main() {
   app.Before = altsrc.InitInputSourceWithContext(flags, altsrc.NewYamlSourceFromFlagFunc("load"))
   app.Flags = flags
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -716,6 +768,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -768,7 +821,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -784,6 +840,7 @@ E.g.
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -806,7 +863,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -832,6 +892,7 @@ may be set by returning a non-nil error that fulfills `cli.ExitCoder`, *or* a
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -852,7 +913,10 @@ func main() {
     return nil
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -872,6 +936,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -903,7 +968,10 @@ func main() {
     },
   }
 
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -943,6 +1011,7 @@ The default bash completion flag (`--generate-bash-completion`) is defined as
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -961,7 +1030,10 @@ func main() {
       Name: "wat",
     },
   }
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -987,6 +1059,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "io"
   "os"
 
@@ -1030,7 +1103,10 @@ VERSION:
     fmt.Println("Ha HA.  I pwnd the help!!1")
   }
 
-  cli.NewApp().Run(os.Args)
+  err := cli.NewApp().Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -1045,6 +1121,7 @@ setting `cli.HelpFlag`, e.g.:
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -1057,7 +1134,10 @@ func main() {
     EnvVar: "SHOW_HALP,HALPPLZ",
   }
 
-  cli.NewApp().Run(os.Args)
+  err := cli.NewApp().Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -1080,6 +1160,7 @@ setting `cli.VersionFlag`, e.g.:
 package main
 
 import (
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -1094,7 +1175,10 @@ func main() {
   app := cli.NewApp()
   app.Name = "partay"
   app.Version = "19.99.0"
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -1109,6 +1193,7 @@ package main
 
 import (
   "fmt"
+  "log"
   "os"
 
   "github.com/urfave/cli"
@@ -1126,7 +1211,10 @@ func main() {
   app := cli.NewApp()
   app.Name = "partay"
   app.Version = "19.99.0"
-  app.Run(os.Args)
+  err := app.Run(os.Args)
+  if err != nil {
+    log.Fatal(err)
+  }
 }
 ```
 
@@ -1388,7 +1476,7 @@ func main() {
     ec := cli.NewExitError("ohwell", 86)
     fmt.Fprintf(c.App.Writer, "%d", ec.ExitCode())
     fmt.Printf("made it!\n")
-    return ec
+    return nil
   }
 
   if os.Getenv("HEXY") != "" {
@@ -1402,7 +1490,9 @@ func main() {
     "whatever-values": 19.99,
   }
 
-  app.Run(os.Args)
+
+  // ignore error so we don't exit non-zero and break gfmrun README example tests
+  _ = app.Run(os.Args)
 }
 
 func wopAction(c *cli.Context) error {