[devbox.json] support env_from dotenv files (#2174)

## Summary
NOTE: Docs update PR will follow.
As per request from users, I added support for `env_from` field being
able to take a path to `*.env` file and have those env variables
available in devbox shell and run.

If a duplicate env variable is specified in both `.env` and in the
`"env"` section of devbox.json, the env section from devbox.json takes
priority and overwrites. This I believe is the correct behavior but I'm
open to discussion.

## How was it tested?
see test file at `testscripts/run/envfrom.test.txt`

Author: mohsenari

internal/devbox/devbox.go

@@ -951,6 +951,21 @@ func (d *Devbox) configEnvs(
 				}
 			}
 		}
+	} else if d.cfg.Root.IsdotEnvEnabled() {
+		// if env_from points to a .env file, parse and add it
+		parsedEnvs, err := d.cfg.Root.ParseEnvsFromDotEnv()
+		if err != nil {
+			// it's fine to include the error ParseEnvsFromDotEnv here because
+			// the error message is relevant to the user
+			return nil, usererr.New(
+				"failed parsing %s file. Error: %v",
+				d.cfg.Root.EnvFrom,
+				err,
+			)
+		}
+		for k, v := range parsedEnvs {
+			env[k] = v
+		}
 	} else if d.cfg.Root.EnvFrom != "" {
 		return nil, usererr.New(
 			"unknown from_env value: %s. Supported value is: %q.",

internal/devconfig/configfile/env.go

@@ -1,6 +1,63 @@
 package configfile
 
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
 func (c *ConfigFile) IsEnvsecEnabled() bool {
-	// envsec for legacy.
-	return c.EnvFrom == "envsec" || c.EnvFrom == "jetpack-cloud"
+	// envsec for legacy. jetpack-cloud for legacy
+	return c.EnvFrom == "envsec" || c.EnvFrom == "jetpack-cloud" || c.EnvFrom == "jetify-cloud"
+}
+
+func (c *ConfigFile) IsdotEnvEnabled() bool {
+	// filename has to end with .env
+	return filepath.Ext(c.EnvFrom) == ".env"
+}
+
+func (c *ConfigFile) ParseEnvsFromDotEnv() (map[string]string, error) {
+	// This check should never happen because we call IsdotEnvEnabled
+	// before calling this method. But having it makes it more robust
+	// in case if anyone uses this method without the IsdotEnvEnabled
+	if !c.IsdotEnvEnabled() {
+		return nil, fmt.Errorf("env file does not have a .env extension")
+	}
+
+	file, err := os.Open(c.EnvFrom)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open file: %s", c.EnvFrom)
+	}
+	defer file.Close()
+
+	envMap := map[string]string{}
+
+	// Read the file line by line
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		// Ideally .env file shouldn't have empty lines and comments but
+		// this check makes it allowed.
+		if strings.TrimSpace(line) == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		parts := strings.SplitN(line, "=", 2)
+		if len(parts) != 2 {
+			return nil, fmt.Errorf("invalid line in .env file: %s", line)
+		}
+		// Also ideally, .env files should not have space in their `key=value` format
+		// but this allows `key = value` to pass through as well
+		key := strings.TrimSpace(parts[0])
+		value := strings.TrimSpace(parts[1])
+
+		// Add the parsed key-value pair to the map
+		envMap[key] = value
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("failed to read env file: %v", err)
+	}
+	return envMap, nil
 }

testscripts/run/envfrom.test.txt

@@ -0,0 +1,36 @@
+# Tests related to setting the env_from for devbox run.
+
+exec devbox run test
+stdout 'BAR'
+
+exec devbox run test2
+stdout 'BAZ'
+
+exec devbox run test3
+stdout 'BAS'
+
+exec devbox run test4
+stdout ''
+
+-- test.env --
+FOO=BAR
+FOO2 = BAZ
+FOO3=ToBeOverwrittenByDevboxJSON
+# FOO4=comment shouldn't be processed
+
+-- devbox.json --
+{
+  "packages": [],
+  "env": {
+    "FOO3": "BAS"
+  },
+  "shell": {
+    "scripts": {
+      "test": "echo $FOO",
+      "test2": "echo $FOO2",
+      "test3": "echo $FOO3",
+      "test4": "echo $FOO4"
+    }
+  },
+  "env_from": "test.env"
+}