fixed missing output if strings have no placeholders

added related tests

README.md

@@ -20,6 +20,9 @@ TESTVAR=foo tg -i /dest/config/file1.ext
 However, using the inline option on your templates will overwrite them.
 It is recommended to use this option on resettable files.
 
+Placeholders which have no corresponding environment variable gets not replaced.
+`echo 'foo {{ NOT_SET }} bar' | ./tg` results in `foo {{ NOT_SET }} bar`
+
 ### TODO
 * flags for file in/out
 * prefix flag for env var e.g. SERVICE_XXX

cli/cli.go

@@ -37,17 +37,26 @@ func main() {
 		rw = bufio.NewReadWriter(bufio.NewReader(os.Stdin), bufio.NewWriter(os.Stdout))
 	}
 
+	replace(rw, file)
+}
+
+func replace(rw *bufio.ReadWriter, file *os.File) {
 	bytes, err := ioutil.ReadAll(rw)
 	must(err)
+	write := func(b []byte) {
+		_, err := rw.Write(b)
+		must(err)
+		must(rw.Flush())
+	}
 
 	if temgo.ContainsVariable(bytes) {
 		str := envVars.ReplaceVariables(bytes)
 		if file != nil {
 			truncate(file)
 		}
-		_, err := rw.Write(str)
-		must(err)
-		must(rw.Flush())
+		write(str)
+	} else if file == nil {
+		write(bytes)
 	}
 }
 

cli/cli_test.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"testing"
+)
+
+func TestReplace(t *testing.T) {
+	wd, _ := os.Getwd()
+	testCases := []struct {
+		in       []byte
+		expected string
+	}{
+		{[]byte("foo bar"), "foo bar"},
+		{[]byte("foo {{ NOT_SET }} bar"), "foo {{ NOT_SET }} bar"},
+		{[]byte("foo {{invalid }} bar"), "foo {{invalid }} bar"},
+		{[]byte("foo {{ PWD }}!"), fmt.Sprintf("foo %s!", wd)},
+	}
+
+	for _, testCase := range testCases {
+		r := bytes.NewBuffer(testCase.in)
+		w := bytes.NewBuffer(make([]byte, 0))
+		rw := bufio.NewReadWriter(bufio.NewReader(r), bufio.NewWriter(w))
+		replace(rw, nil)
+		out := w.Bytes()
+		if string(out) != testCase.expected {
+			t.Errorf("\nWant: \t%q\nGot: \t%q", string(testCase.expected), string(out))
+		}
+	}
+}

temgo/temgo.go

@@ -17,7 +17,11 @@ func ContainsVariable(str []byte) bool {
 func replace(e *EnvVars, bytes []byte) []byte {
 	list := templatePattern.FindAllStringSubmatch(string(bytes), -1)
 	for _, match := range list {
-		bytes = []byte(strings.Replace(string(bytes), match[0], (*e)[match[1]], -1))
+		str, ok := (*e)[match[1]]
+		if !ok {
+			continue // variable not set
+		}
+		bytes = []byte(strings.Replace(string(bytes), match[0], str, -1))
 	}
 	return bytes
 }