⚡ Bolt: Stop rebuilding the HTML-escape replacers on every ASCII screen capture

[jnnngs]

💡 What

escapeAttr and escapeText in connect3270/emulator.go each built a brand new *strings.Replacer on every single call, even though their replacement tables (&→&, <→<, >→>, and the attribute variant adding "→") are constant. Both replacers are now hoisted to package-level vars (htmlAttrEscaper, htmlTextEscaper) built once at init.

🎯 Why

• escapeText runs once per non-API AsciiScreenGrab call, over the entire captured screen's text — and AsciiScreenGrab is a workflow step that runs once per step, per worker, in a concurrent load test (-concurrent N).
• escapeAttr runs up to a handful of times per capture too (once per non-empty data-port / data-host / data-type attribute via captureAttrs).
• *strings.Replacer is documented as safe for concurrent use, so there's no correctness reason to rebuild it per call — it was just wasted allocation on a table that never changes, repeated on a per-workflow-step hot path.

📊 Impact

Confirmed with a synthetic benchmark (~2000-byte screen, representative of an 80×24 capture):

	old (per-call NewReplacer)	new (hoisted)
allocs/op	9	2
B/op	~14952	~8192 (~45% less)
ns/op	~23165	~20032 (~13% faster)

No algorithmic complexity change — this is a pure allocation/GC-pressure reduction on a per-call basis, which compounds under -concurrent load testing where many workers hit AsciiScreenGrab repeatedly.

🔬 Measurement

// connect3270/zzbench_test.go (not committed — for local verification only)
func BenchmarkEscapeTextOld(b *testing.B) {
	s := strings.Repeat("data <foo> & <bar> ", 100)
	for i := 0; i < b.N; i++ {
		replacer := strings.NewReplacer("&", "&amp;", "<", "&lt;", ">", "&gt;")
		_ = replacer.Replace(s)
	}
}

func BenchmarkEscapeTextNew(b *testing.B) {
	s := strings.Repeat("data <foo> & <bar> ", 100)
	for i := 0; i < b.N; i++ {
		_ = escapeText(s)
	}
}

Run with go test -bench=BenchmarkEscapeText -benchmem -run=^$ ./connect3270/.

Verified locally:

• go vet ./... — clean
• go test -short ./... — all packages pass
• go test -run TestCompat -v ./connect3270/ — all 17 compat tests pass (embedded emulator was available in this environment)

No behavior change: output of escapeAttr/escapeText is byte-for-byte identical to before.

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🤖 Generated with Claude Code

https://claude.ai/code/session_015CPbfGS3iGtSU6YU2ZLtgP

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Generated by Claude Code