mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-24 06:14:01 +08:00
Chris Tate
52459a86d4
* feat(compiler): lower stored text codec calls - Lower same-scope const TextEncoder and TextDecoder call receivers without runtime instances. - Preserve fences for escaping, captured, and imported codec values with actionable diagnostics. - Add differential, diagnostic, and preflight baseline coverage for the supported idiom. * fix(compiler): fence deferred text codec calls * fix text codec switch-clause TDZ handling
54 lines
2.5 KiB
TypeScript
54 lines
2.5 KiB
TypeScript
// The WHATWG encoder pair, composed and same-scope const store-then-call:
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// utf-8 round trips, BOM stripping, and maximal-subpart replacement,
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// byte-compared against Node.
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const enc = new TextEncoder().encode("héllo😀");
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console.log(enc.length, enc[0], enc[1], enc[2], enc[6]);
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console.log(new TextDecoder().decode(enc));
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// A leading BOM strips (Buffer.toString("utf8") keeps it — the one
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// behavioral difference between the two decodes).
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console.log(new TextDecoder().decode(new Uint8Array([0xef, 0xbb, 0xbf, 0x41, 0x42])));
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console.log(new TextDecoder().decode(new Uint8Array([0xef, 0xbb, 0xbf])).length);
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console.log(Buffer.from([0xef, 0xbb, 0xbf, 0x41]).toString("utf8").length);
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// Invalid sequences replace per maximal subpart, exactly like Node.
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console.log(JSON.stringify(new TextDecoder().decode(new Uint8Array([0x41, 0xff, 0x42]))));
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console.log(JSON.stringify(new TextDecoder().decode(new Uint8Array([0xf0, 0x9f, 0x98]))));
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// Zero-argument decode is "" per spec; the explicit utf-8 label works.
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console.log(new TextDecoder().decode().length);
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console.log(new TextDecoder("utf-8").decode(Buffer.from("hi", "utf8")));
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// Round trip through both, Buffer input included.
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const rt = new TextDecoder().decode(new TextEncoder().encode("round ✓ trip"));
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console.log(rt === "round ✓ trip", rt);
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console.log(new TextEncoder().encode("").length);
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// The ordinary stored-instance idiom is compile-time alias plumbing: the
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// default constructors have no effects, and supported calls resolve back
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// through a stable const without materializing the codec object.
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const encoder = new TextEncoder();
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const decoder = new TextDecoder();
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const stored = encoder.encode("stored héllo 😀");
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console.log(stored.length, decoder.decode(stored));
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console.log(encoder.encode("again").length, decoder.decode(Buffer.from("twice", "utf8")));
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// An explicit literal utf-8 label is equally effect-free. Function-local
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// bindings take the same rewrite within their own execution scope.
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function localRoundTrip(s: string): string {
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const labelledDecoder = new TextDecoder("utf-8");
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const localEncoder = new TextEncoder();
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return labelledDecoder.decode(localEncoder.encode(s));
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}
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console.log(localRoundTrip("local ✓"));
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// A switch clause is still one straight-line execution region: the
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// declaration dominates the call when both live in that clause.
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const codecCase = 1;
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switch (codecCase) {
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case 1:
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const caseEncoder = new TextEncoder();
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console.log(caseEncoder.encode("same clause").length);
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break;
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}
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