consolidate env handling into pkg/env

Env-variable related code is scattered across several packages making it
hard to maintain and extend.  Consolidate the code into a new pkg/env
package.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 126 insertions, 0 deletions

diff --git a/pkg/env/env.go b/pkg/env/env.go
new file mode 100644
index 000000000..31ffab03c
--- /dev/null
+++ b/pkg/env/env.go
@@ -0,0 +1,126 @@
+// Package for processing environment variables.
+package env
+
+// TODO: we need to add tests for this package.
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+// DefaultEnvVariables set $PATH, $TERM and $container.
+var DefaultEnvVariables = map[string]string{
+	"PATH":      "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+	"TERM":      "xterm",
+	"container": "podman",
+}
+
+const whiteSpaces = " \t"
+
+// ParseSlice parses the specified slice and transforms it into an environment
+// map.
+func ParseSlice(s []string) (map[string]string, error) {
+	env := make(map[string]string, len(s))
+	for _, e := range s {
+		if err := parseEnv(env, e); err != nil {
+			return nil, err
+		}
+	}
+	return env, nil
+}
+
+// Slice transforms the specified map of environment variables into a
+// slice. If a value is non-empty, the key and value are joined with '='.
+func Slice(m map[string]string) []string {
+	env := make([]string, len(m))
+	for k, v := range m {
+		var s string
+		if len(v) > 0 {
+			s = fmt.Sprintf("%s=%s", k, v)
+		} else {
+			s = k
+		}
+		env = append(env, s)
+	}
+	return env
+}
+
+// Join joins the two environment maps with override overriding base.
+func Join(base map[string]string, override map[string]string) map[string]string {
+	if len(base) == 0 {
+		return override
+	}
+	for k, v := range override {
+		base[k] = v
+	}
+	return base
+}
+
+// ParseFile parses the specified path for environment variables and returns them
+// as a map.
+func ParseFile(path string) (env map[string]string, err error) {
+	defer func() {
+		if err != nil {
+			err = errors.Wrapf(err, "error parsing env file %q", path)
+		}
+	}()
+
+	fh, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer fh.Close()
+
+	scanner := bufio.NewScanner(fh)
+	for scanner.Scan() {
+		// trim the line from all leading whitespace first
+		line := strings.TrimLeft(scanner.Text(), whiteSpaces)
+		// line is not empty, and not starting with '#'
+		if len(line) > 0 && !strings.HasPrefix(line, "#") {
+			if err := parseEnv(env, line); err != nil {
+				return nil, err
+			}
+		}
+	}
+	return env, scanner.Err()
+}
+
+func parseEnv(env map[string]string, line string) error {
+	data := strings.SplitN(line, "=", 2)
+
+	// catch invalid variables such as "=" or "=A"
+	if data[0] == "" {
+		return errors.Errorf("invalid environment variable: %q", line)
+	}
+
+	// trim the front of a variable, but nothing else
+	name := strings.TrimLeft(data[0], whiteSpaces)
+	if strings.ContainsAny(name, whiteSpaces) {
+		return errors.Errorf("name %q has white spaces, poorly formatted name", name)
+	}
+
+	if len(data) > 1 {
+		env[name] = data[1]
+	} else {
+		if strings.HasSuffix(name, "*") {
+			name = strings.TrimSuffix(name, "*")
+			for _, e := range os.Environ() {
+				part := strings.SplitN(e, "=", 2)
+				if len(part) < 2 {
+					continue
+				}
+				if strings.HasPrefix(part[0], name) {
+					env[part[0]] = part[1]
+				}
+			}
+		} else if val, ok := os.LookupEnv(name); ok {
+			// if only a pass-through variable is given, clean it up.
+			env[name] = val
+		}
+	}
+	return nil
+}