[envvars] Fix error when env contains Bash function (#2612)

## Summary

Fixes #995 - Error running `devbox shell` in environment with exported
Bash function

## How was it tested?

Tested that when running the below commands:

- no errors are printed
- the `foo` function runs successfully and prints `foo`

Case 1 (simple):
```
foo() { echo foo; }
export -f foo
devbox shell
foo
```

Case 2 (function that contains special characters `"` and `$`):
```
foo() { echo "${bar}"; }
export -f foo
export bar=foo
devbox shell
foo
```

Case 3 (`shellenv`):

```
foo() { echo foo; }
export -f foo
devbox shellenv > shellrc

# open a new shell

source shellrc
foo
```

Also added a Bash function to the test data used by
`TestWriteDevboxShellrc`.

## Community Contribution License

All community contributions in this pull request are licensed to the
project
maintainers under the terms of the
[Apache 2 License](https://www.apache.org/licenses/LICENSE-2.0).

By creating this pull request, I represent that I have the right to
license the
contributions to the project maintainers under the Apache 2 License as
stated in
the
[Community Contribution
License](https://github.com/jetify-com/opensource/blob/main/CONTRIBUTING.md#community-contribution-license).

Author: apgrucza

internal/devbox/envvars.go

@@ -29,20 +29,33 @@ func exportify(vars map[string]string) string {
 	slices.Sort(keys) // for reproducibility
 
 	strb := strings.Builder{}
-	for _, k := range keys {
-		strb.WriteString("export ")
-		strb.WriteString(k)
-		strb.WriteString(`="`)
-		for _, r := range vars[k] {
-			switch r {
-			// Special characters inside double quotes:
-			// https://pubs.opengroup.org/onlinepubs/009604499/utilities/xcu_chap02.html#tag_02_02_03
-			case '$', '`', '"', '\\', '\n':
-				strb.WriteRune('\\')
+	for _, key := range keys {
+		if strings.HasPrefix(key, "BASH_FUNC_") && strings.HasSuffix(key, "%%") {
+			// Bash function
+			funcName := strings.TrimSuffix(key, "%%")
+			funcName = strings.TrimPrefix(funcName, "BASH_FUNC_")
+			strb.WriteString(funcName)
+			strb.WriteString(" ")
+			strb.WriteString(vars[key])
+			strb.WriteString("\nexport -f ")
+			strb.WriteString(funcName)
+			strb.WriteString("\n")
+		} else {
+			// Regular variable
+			strb.WriteString("export ")
+			strb.WriteString(key)
+			strb.WriteString(`="`)
+			for _, r := range vars[key] {
+				switch r {
+				// Special characters inside double quotes:
+				// https://pubs.opengroup.org/onlinepubs/009604499/utilities/xcu_chap02.html#tag_02_02_03
+				case '$', '`', '"', '\\', '\n':
+					strb.WriteRune('\\')
+				}
+				strb.WriteRune(r)
 			}
-			strb.WriteRune(r)
+			strb.WriteString("\";\n")
 		}
-		strb.WriteString("\";\n")
 	}
 	return strings.TrimSpace(strb.String())
 }

internal/devbox/testdata/shellrc/basic/env

@@ -2,3 +2,4 @@ simple=value
 space=quote me
 quote=they said, "lasers"
 special=$`"\
+BASH_FUNC_echo_simple%%=() { echo "${simple}"; }

internal/devbox/testdata/shellrc/basic/shellrc.golden

@@ -3,6 +3,8 @@ if [ -f testdata/shellrc/basic/shellrc ]; then
 fi
 # Begin Devbox Post-init Hook
 
+echo_simple () { echo "${simple}"; }
+export -f echo_simple
 export quote="they said, \"lasers\"";
 export simple="value";
 export space="quote me";