complete: enable complete.Complete() output capturing (#138)

* complete: test capturing Complete() output

Implement an Example test to demonstrate capturing the output
of Complete(), which is crucial for integration tests.

* complete: do not hard-code the I/O streams at the package initialization

Instead of defining the input/output streams as unexported global vars
that only get their values assigned to once, at the very initialization
of the package, use the values that `os.Stdin` and `os.Stdout` have at
the particular moment on every `complete.Complete()` call.

Fix #137

* complete: capture and discard output in TestComplete

Restore earlier behavior using proper stream redirection this time.

* complete: output capturing example: define things in the package scope

Define the `stringLookup` func type and `promptEnv` func in the package
scope instead of the `ExampleComplete_outputCapturing` test.

* complete: rename the `stringLookup` func type to `getEnvFn`

1 files changed, 6 insertions, 4 deletions

diff --git a/complete.go b/complete.go
index 2a4c905..0641c39 100644
--- a/complete.go
+++ b/complete.go
@@ -49,10 +49,8 @@ func (p PredictFunc) Predict(prefix string) []string {
 }
 
 var (
-	getEnv           = os.Getenv
-	exit             = os.Exit
-	out    io.Writer = os.Stdout
-	in     io.Reader = os.Stdin
+	getEnv = os.Getenv
+	exit   = os.Exit
 )
 
 // Complete the command line arguments for the given command in the case that the program
@@ -66,6 +64,10 @@ func Complete(name string, cmd Completer) {
 		doUninstall = getEnv("COMP_UNINSTALL") == "1"
 		yes         = getEnv("COMP_YES") == "1"
 	)
+	var (
+		out io.Writer = os.Stdout
+		in  io.Reader = os.Stdin
+	)
 	if doInstall || doUninstall {
 		install.Run(name, doUninstall, yes, out, in)
 		exit(0)