fix(shellenv): don't escape newlines in exported env var values (#2814)

[mikeland73]

Summary

Fixes #2814.

eval "$(devbox global shellenv)" could print bash: 1__bp_interactive_mode: ambiguous redirect at every prompt when an environment variable (e.g. a PROMPT_COMMAND set by bash-preexec) contained newlines.

Root cause

exportify (internal/devbox/envvars.go) emits each variable as export KEY="value";, escaping special characters inside the double quotes. It escaped \n by writing a backslash before the newline, producing \<newline>:

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

Inside double quotes the shell treats a backslash-newline as a line continuation and removes it entirely, collapsing a multi-line value onto one line. A bare newline inside double quotes is already literal, so the escaping was both unnecessary and corrupting.

For the reporter's PROMPT_COMMAND, the lines ... >/dev/null 2>&1 and __bp_interactive_mode were joined into ... 2>&1__bp_interactive_mode, so the 2>&1 redirect target became 1__bp_interactive_mode — hence the "ambiguous redirect" error.

Minimal demonstration of the shell behavior:

$ eval 'export A="line1\
2>&1\
tail"'; printf '[%s]\n' "$A"
[line12>&1tail]          # backslash-newline (old behavior) — corrupted

$ eval 'export B="line1
2>&1
tail"'; printf '[%s]\n' "$B"
[line1
2>&1
tail]                   # bare newline (new behavior) — correct

Fix

Drop \n from the set of characters escaped inside double quotes, so newlines are emitted literally. The exportifyNushell path already emits newlines literally, so this makes the two consistent.

How was it tested?

• Added TestExportifyPreservesNewlines, which pins the multi-line output and asserts no \<newline> line-continuation is produced.
• go test ./internal/devbox/ -run 'TestExportify|TestIsValidEnvName' — passes.
• gofmt -l and go vet ./internal/devbox/ — clean.

/cc @proedie (issue reporter) — thanks for the precise diagnosis and workaround in the report.

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maintainers under the terms of the
Apache 2 License.

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https://claude.ai/code/session_01WzomNNnDLmX4LMZ4aPtYvm

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Generated by Claude Code

[Copilot]

Pull request overview

This PR fixes a shellenv corruption bug where exportify escaped \n inside double-quoted values as \<newline>, which Bash interprets as a line continuation and strips—collapsing multiline env var values (notably PROMPT_COMMAND) and triggering errors like “ambiguous redirect”.

Changes:

• Stop escaping newline characters in internal/devbox/envvars.go when emitting export KEY="value";.
• Add a regression test to ensure multiline values are preserved and no \\\n line-continuation sequence is produced.

Reviewed changes

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

File	Description
internal/devbox/envvars.go	Removes newline from the set of escaped characters in exportify, with clarifying commentary about shell semantics.
internal/devbox/envvars_test.go	Adds TestExportifyPreservesNewlines to lock in correct multiline export behavior and prevent regressions.

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