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Iterates over configured cheatpaths and runs git pull on each one that is a git repository with a clean worktree. Supports SSH remotes via key file discovery and SSH agent fallback. Works with --path filtering. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
100 lines
3.2 KiB
Markdown
100 lines
3.2 KiB
Markdown
# ADR-002: No Defensive Checks for Environment Variable Parsing
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Date: 2025-01-21
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## Status
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Accepted
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## Context
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In the `EnvVars()` function in `internal/config/env.go`, the code parses environment variables assuming they all contain an equals sign:
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```go
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for _, e := range os.Environ() {
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pair := strings.SplitN(e, "=", 2)
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if runtime.GOOS == "windows" {
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pair[0] = strings.ToUpper(pair[0])
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}
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envvars[pair[0]] = pair[1] // Could panic if pair has < 2 elements
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}
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```
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If `os.Environ()` returned a string without an equals sign, `strings.SplitN` would return a slice with only one element, causing a panic when accessing `pair[1]`.
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## Decision
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We will **not** add defensive checks for this condition. The current code that assumes all environment strings contain "=" will remain unchanged.
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## Rationale
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### Go Runtime Guarantees
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Go's official documentation guarantees that `os.Environ()` returns environment variables in the form "key=value". This is a documented contract of the Go runtime that has been stable since Go 1.0.
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### Empirical Evidence
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Testing across platforms confirms:
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- All environment variables returned by `os.Environ()` contain at least one "="
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- Empty environment variables appear as "KEY=" (with an empty value)
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- Even Windows special variables like "=C:=C:\path" maintain the format
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### Cost-Benefit Analysis
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Adding defensive code would:
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- **Cost**: Add complexity and cognitive overhead
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- **Cost**: Suggest uncertainty about Go's documented behavior
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- **Cost**: Create dead code that can never execute under normal conditions
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- **Benefit**: Protect against a theoretical scenario that violates Go's guarantees
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The only scenarios where this could panic are:
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1. A bug in Go's runtime (extremely unlikely, would affect all Go programs)
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2. Corrupted OS-level environment (would cause broader system issues)
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3. Breaking change in future Go version (would break many programs, unlikely)
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## Consequences
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### Positive
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- Simpler, more readable code
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- Trust in platform guarantees reduces unnecessary defensive programming
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- No performance overhead from unnecessary checks
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### Negative
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- Theoretical panic if Go's guarantees are violated
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### Neutral
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- Follows Go community standards of trusting standard library contracts
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## Alternatives Considered
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### 1. Add Defensive Check
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```go
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if len(pair) < 2 {
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continue // or pair[1] = ""
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}
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```
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**Rejected**: Adds complexity for a condition that should never occur.
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### 2. Add Panic with Clear Message
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```go
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if len(pair) < 2 {
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panic("os.Environ() contract violation: " + e)
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}
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```
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**Rejected**: Would crash the program for the same theoretical issue.
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### 3. Add Comment Documenting Assumption
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```go
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// os.Environ() guarantees "key=value" format, so pair[1] is safe
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envvars[pair[0]] = pair[1]
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```
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**Rejected**: While documentation is good, this particular guarantee is fundamental to Go.
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## Notes
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If Go ever changes this behavior (extremely unlikely as it would break compatibility), it would be caught immediately in testing as the program would panic on startup. This would be a clear signal to revisit this decision.
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## References
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- Go os.Environ() documentation: https://pkg.go.dev/os#Environ
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- Go os.Environ() source code and tests |