fix(shellenv): preserve literal newlines in exported env values (ambiguous redirect)

[mikeland73]

Summary

Fixes #2814.

eval "$(devbox global shellenv)" produced the following error on every new prompt for users whose shell sets a multi-line PROMPT_COMMAND (e.g. via bash-preexec, as the elementary OS terminal does):

bash: 1__bp_interactive_mode: ambiguous redirect

Root cause

exportify (internal/devbox/envvars.go) builds export KEY="value"; statements and escaped newlines inside the value by writing a backslash before the newline:

case '$', '`', '"', '\\', '\n':
    strb.WriteRune('\\')

Inside a bash double-quoted string, a backslash-newline is a line continuation: the shell removes both the backslash and the newline and joins the adjacent lines. So a multi-line value like:

__bp_precmd_invoke_cmd
dbus-send ... >/dev/null 2>&1
__bp_interactive_mode

was emitted as ... 2>&1\<newline>__bp_interactive_mode and collapsed by the shell into ... 2>&1__bp_interactive_mode. The redirect target became 1__bp_interactive_mode, hence the ambiguous redirect error.

Newlines are not special inside double quotes (see the POSIX shell quoting rules already cited in the code) — they are preserved literally. The fix is simply to stop escaping them.

Quick demonstration of the difference:

$ eval 'X="a 2>&1\
__bp"'; printf '[%s]\n' "$X"
[a 2>&1__bp]          # old behavior: newline eaten, lines joined

$ eval 'X="a 2>&1
__bp"'; printf '[%s]\n' "$X"
[a 2>&1
__bp]                # new behavior: newline preserved

Changes

• internal/devbox/envvars.go: drop '\n' from the set of characters exportify escapes, with a comment explaining why newlines must stay literal. The other shell-special characters ($, `, ", \) are still escaped.
• internal/devbox/envvars_test.go: new TestExportify covering simple values, special-character escaping, and the multi-line regression from this issue.

This affects both devbox shellenv output and the env exports written into the generated shellrc; in both contexts the output is sourced as bash, so literal newlines inside double quotes are correct.

How was it tested?

• go test ./internal/devbox/ -run TestExportify -v — passes.
• go build ./internal/devbox/ and go vet ./internal/devbox/ — clean.
• Verified the bash line-continuation behavior directly (see demonstration above).

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cc @proedie (reporter) — thanks for the detailed write-up and the precise pinpointing of the offending line; that made this a quick fix.

🤖 Generated with Claude Code

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Generated by Claude Code

[Copilot]

Pull request overview

Fixes a bash quoting bug in devbox global shellenv / generated shellrc exports where multi-line environment values (notably PROMPT_COMMAND) were being mangled due to emitting backslash-newline sequences inside double quotes, which bash treats as a line continuation and removes.

Changes:

• Stop escaping '\n' in exportify so multi-line env values preserve literal newlines inside double quotes.
• Add focused unit tests for exportify, including special-character escaping and the multi-line regression from #2814.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/devbox/envvars.go	Updates bash export escaping rules to preserve literal newlines in double-quoted values, avoiding line-continuation behavior.
internal/devbox/envvars_test.go	Adds TestExportify to cover simple exports, special-character escaping, and the multi-line newline-preservation regression.

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