feat(climatecontrol): initial working version

climatecontrol.go

@@ -0,0 +1,77 @@
+// Package climatecontrol provides test helper functions which temporary changes
+// environment variables accessible via os.Getenv and os.LookupEnv. After they
+// are done, all changes to environment variables are reset.
+package climatecontrol
+
+import (
+	"os"
+	"strings"
+	"sync"
+)
+
+var mux = &sync.Mutex{}
+
+// WithEnv temporarily sets all given vars as environment variables during the
+// execution of f function. Existing environment variables are also available
+// within f. Any overridden environment variables will contain the overridden
+// value..
+//
+// After f execution completes all changes to environment variables are reset,
+// including manual changes within the f function.
+func WithEnv(vars map[string]string, f func()) {
+	mux.Lock()
+	defer mux.Unlock()
+
+	undo := parseEnviron(os.Environ())
+
+	apply(vars)
+	defer func() {
+		os.Clearenv()
+		apply(undo)
+	}()
+
+	f()
+}
+
+// WithCleanEnv temporarily changes all environment variables available within f
+// function to only be those provided. Existing environment variables are not
+// available within f.
+//
+// After f execution completes all changes to environment variables are reset,
+// including manual changes within the f function.
+func WithCleanEnv(vars map[string]string, f func()) {
+	mux.Lock()
+	defer mux.Unlock()
+
+	undo := parseEnviron(os.Environ())
+
+	os.Clearenv()
+	apply(vars)
+	defer func() {
+		os.Clearenv()
+		apply(undo)
+	}()
+
+	f()
+}
+
+func apply(vars map[string]string) {
+	for k, v := range vars {
+		os.Setenv(k, v)
+	}
+}
+
+func parseEnviron(vars []string) map[string]string {
+	r := map[string]string{}
+
+	for _, v := range vars {
+		i := strings.Index(v, "=")
+		if i < 1 {
+			continue
+		}
+
+		r[v[0:i]] = v[i+1:]
+	}
+
+	return r
+}