flagenv, use it, legal reworkings

4 files changed, 215 insertions, 0 deletions

diff --git a/internal/flagenv/LICENSE b/internal/flagenv/LICENSE
new file mode 100644
index 0000000..bde9055
--- /dev/null
+++ b/internal/flagenv/LICENSE
@@ -0,0 +1,30 @@
+BSD License
+
+For flagenv software
+
+Copyright (c) 2015, Facebook, Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * Neither the name Facebook nor the names of its contributors may be used to
+   endorse or promote products derived from this software without specific
+   prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\ No newline at end of file
diff --git a/internal/flagenv/flagenv.go b/internal/flagenv/flagenv.go
new file mode 100644
index 0000000..fe2ea8d
--- /dev/null
+++ b/internal/flagenv/flagenv.go
@@ -0,0 +1,67 @@
+// Package flagenv provides the ability to populate flags from
+// environment variables.
+package flagenv
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+)
+
+// Specify a prefix for environment variables.
+var Prefix = ""
+
+func contains(list []*flag.Flag, f *flag.Flag) bool {
+	for _, i := range list {
+		if i == f {
+			return true
+		}
+	}
+	return false
+}
+
+// ParseSet parses the given flagset. The specified prefix will be applied to
+// the environment variable names.
+func ParseSet(prefix string, set *flag.FlagSet) error {
+	var explicit []*flag.Flag
+	var all []*flag.Flag
+	set.Visit(func(f *flag.Flag) {
+		explicit = append(explicit, f)
+	})
+
+	var err error
+	set.VisitAll(func(f *flag.Flag) {
+		if err != nil {
+			return
+		}
+		all = append(all, f)
+		if !contains(explicit, f) {
+			name := strings.Replace(f.Name, ".", "_", -1)
+			name = strings.Replace(name, "-", "_", -1)
+			if prefix != "" {
+				name = prefix + name
+			}
+			name = strings.ToUpper(name)
+			val := os.Getenv(name)
+			if val != "" {
+				if ferr := f.Value.Set(val); ferr != nil {
+					err = fmt.Errorf("failed to set flag %q with value %q", f.Name, val)
+				}
+			}
+		}
+	})
+	return err
+}
+
+// Parse will set each defined flag from its corresponding environment
+// variable . If dots or dash are presents in the flag name, they will be
+// converted to underscores.
+//
+// If Parse fails, a fatal error is issued.
+func Parse() {
+	if err := ParseSet(Prefix, flag.CommandLine); err != nil {
+		log.Fatalln(err)
+	}
+}
diff --git a/internal/flagenv/flagenv_test.go b/internal/flagenv/flagenv_test.go
new file mode 100644
index 0000000..4ff958b
--- /dev/null
+++ b/internal/flagenv/flagenv_test.go
@@ -0,0 +1,82 @@
+package flagenv_test
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+	"testing"
+
+	"github.com/Xe/x/internal/flagenv"
+	"github.com/facebookgo/ensure"
+)
+
+func named(t, v string) string { return strings.ToUpper(t + v) }
+
+func ExampleParse() {
+	var raz string
+	flag.StringVar(&raz, "raz-value", "bar", "set the raz")
+
+	// override default flag value with value found in MY_RAZ_VALUE
+	flagenv.Prefix = "my_"
+	flagenv.Parse()
+
+	// override value found in MY_RAZ_VALUE with command line flag value -raz-value=foo
+	flag.Parse()
+}
+
+func TestNothingToDo(t *testing.T) {
+	const name = "TestNothingToDo"
+	s := flag.NewFlagSet(name, flag.PanicOnError)
+	s.String(named(name, "foo"), "", "")
+	ensure.Nil(t, flagenv.ParseSet(name, s))
+}
+
+func TestAFewFlags(t *testing.T) {
+	const name = "TestAFewFlags"
+	s := flag.NewFlagSet(name, flag.PanicOnError)
+	const foo = "42"
+	const bar = int(43)
+	fooActual := s.String("foo", "", "")
+	barActual := s.Int("bar", 0, "")
+	os.Setenv(named(name, "foo"), foo)
+	os.Setenv(named(name, "bar"), fmt.Sprint(bar))
+	ensure.Nil(t, flagenv.ParseSet(name, s))
+	ensure.DeepEqual(t, *fooActual, foo)
+	ensure.DeepEqual(t, *barActual, bar)
+}
+
+func TestInvalidFlagValue(t *testing.T) {
+	const name = "TestInvalidFlagValue"
+	s := flag.NewFlagSet(name, flag.PanicOnError)
+	s.Int("bar", 0, "")
+	os.Setenv(named(name, "bar"), "a")
+	ensure.Err(t, flagenv.ParseSet(name, s),
+		regexp.MustCompile(`failed to set flag "bar" with value "a"`))
+}
+
+func TestReturnsFirstError(t *testing.T) {
+	const name = "TestReturnsFirstError"
+	s := flag.NewFlagSet(name, flag.PanicOnError)
+	s.Int("bar1", 0, "")
+	s.Int("bar2", 0, "")
+	os.Setenv(named(name, "bar1"), "a")
+	ensure.Err(t, flagenv.ParseSet(name, s),
+		regexp.MustCompile(`failed to set flag "bar1" with value "a"`))
+}
+
+func TestExplicitAreIgnored(t *testing.T) {
+	const name = "TestExplicitAreIgnored"
+	s := flag.NewFlagSet(name, flag.PanicOnError)
+	const bar = int(43)
+	barActual := s.Int("bar", 0, "")
+	s.Parse([]string{"-bar", fmt.Sprint(bar)})
+	os.Setenv(named(name, "bar"), "44")
+	ensure.Nil(t, flagenv.ParseSet(name, s))
+	ensure.DeepEqual(t, *barActual, bar)
+}
+
+func TestGlobalParse(t *testing.T) {
+	flagenv.Parse()
+}
diff --git a/internal/flagenv/legal.go b/internal/flagenv/legal.go
new file mode 100644
index 0000000..41bf559
--- /dev/null
+++ b/internal/flagenv/legal.go
@@ -0,0 +1,36 @@
+package flagenv
+
+import "go4.org/legal"
+
+func init() {
+	legal.RegisterLicense(`BSD License
+
+For flagenv software
+
+Copyright (c) 2015, Facebook, Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * Neither the name Facebook nor the names of its contributors may be used to
+   endorse or promote products derived from this software without specific
+   prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.`)
+}