Implement compilation transforms

installer/transforms.go

@@ -0,0 +1,26 @@
+package installer
+
+import (
+	"bytes"
+	"os"
+	"regexp"
+)
+
+var shebangRegex = regexp.MustCompile("^#!.*\n")
+
+// trimShebang removes leading shebangs from a byte slice.
+func trimShebang(d []byte) []byte {
+	return shebangRegex.ReplaceAll(d, []byte{})
+}
+
+// trimWhitespace removes whitespace before and after a byte slice.
+func trimWhitespace(d []byte) []byte {
+	return bytes.Trim(d, "\n\t ")
+}
+
+var envGetter = os.Getenv
+
+// expandEnvironment replaces environment variables.
+func expandEnvironment(d []byte) []byte {
+	return []byte(os.Expand(string(d), envGetter))
+}

installer/transforms_test.go

@@ -0,0 +1,70 @@
+package installer
+
+import (
+	"testing"
+)
+
+func TestTrimWhitespace(t *testing.T) {
+	testCases := []struct {
+		input    string
+		expected string
+	}{
+		{"Nothing to trim", "Nothing to trim"},
+		{"  \n\nOne Two \n ", "One Two"},
+	}
+
+	for _, testCase := range testCases {
+		actual := trimWhitespace([]byte(testCase.input))
+
+		if string(actual) != testCase.expected {
+			t.Errorf("Expected string = %s; got string = %s", testCase.expected, actual)
+		}
+	}
+}
+
+func TestTrimShebang(t *testing.T) {
+	testCases := []struct {
+		input    string
+		expected string
+	}{
+		{"#!/bin/bash\ncode", "code"},
+		{"code\n#!/bin/bash\ncode", "code\n#!/bin/bash\ncode"},
+	}
+
+	for _, testCase := range testCases {
+		actual := trimShebang([]byte(testCase.input))
+
+		if string(actual) != testCase.expected {
+			t.Errorf("Expected string = %s; got string = %s", testCase.expected, actual)
+		}
+	}
+}
+
+func TestExpandEnvironment(t *testing.T) {
+	envMap := map[string]string{
+		"VARIABLE": "myVariable",
+	}
+
+	testCases := []struct {
+		input    string
+		expected string
+	}{
+		{"Testing ${VARIABLE}", "Testing myVariable"},
+		{"testing ${INVALID}", "testing "},
+	}
+
+	origEnvGetter := envGetter
+	defer func() { envGetter = origEnvGetter }()
+
+	envGetter = func(key string) string {
+		return envMap[key]
+	}
+
+	for _, testCase := range testCases {
+		actual := expandEnvironment([]byte(testCase.input))
+
+		if string(actual) != testCase.expected {
+			t.Errorf("Expected string = %s; got string = %s", testCase.expected, actual)
+		}
+	}
+}