71 lines
2.9 KiB
TypeScript
71 lines
2.9 KiB
TypeScript
// https://github.com/oven-sh/bun/issues/31002
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//
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// `if (0) var []` (a destructuring `var` with zero bindings inside a
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// statically-dead branch) panicked the printer with
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// `panic: internal error: entered unreachable code` at
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// `src/js_printer/lib.rs:2308`. The printer asserts that a `var` decl list
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// is never empty ("var;" is invalid syntax). The dead-code elimination
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// pass in `scan_side_effects.rs::should_keep_stmt_in_dead_control_flow`
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// hoists identifiers out of destructuring patterns to preserve `var`
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// hoisting semantics; when the pattern binds no identifiers (`var []`,
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// `var {}`) the list collapsed to empty but the statement was still
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// kept, tripping the printer invariant in the next pass.
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//
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// The fix: when the hoisted identifiers vector is empty, drop the whole
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// statement. There is nothing to hoist and no valid `var` output exists.
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//
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// Run in a subprocess so a reintroduction (panic in the child) doesn't
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// tear down the in-process test runner.
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import { expect, test } from "bun:test";
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import { bunEnv, bunExe } from "harness";
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test.concurrent.each([
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// Bare `var []` / `var {}` as the only statement in a dead `if` body.
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// These were the exact forms in the bug report; without the fix, each
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// one crashed the printer.
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"if(0)var[]",
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"if(0)var{}",
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// Same empty destructuring inside a function body — the DCE path runs
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// per-scope and must not crash regardless of enclosing scope.
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"function f(){if(0)var[]}",
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])("`%s` does not crash the printer (dead-branch destructuring var with no bindings)", async source => {
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await using proc = Bun.spawn({
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cmd: [bunExe(), "-e", source],
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env: bunEnv,
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stdin: "ignore",
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stdout: "pipe",
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stderr: "pipe",
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timeout: 10_000,
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});
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const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
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// Before the fix: stderr carried `panic: internal error: entered
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// unreachable code` and the process exited with a crash signal.
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// After the fix: the dead branch is dropped and the program exits 0
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// with no output.
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expect(stdout).toBe("");
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expect(stderr).toBe("");
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expect(proc.signalCode).toBeNull();
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expect(exitCode).toBe(0);
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});
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test.concurrent("dead-branch destructuring with real identifiers still hoists them as `undefined`", async () => {
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// Regression guard: the fix must not drop destructuring `var`s that do
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// introduce bindings — those still need to be hoisted so that reads
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// after the dead `if` see `undefined` (not ReferenceError).
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await using proc = Bun.spawn({
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cmd: [bunExe(), "-e", "if(0) var [a, b] = []; console.log(typeof a, typeof b);"],
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env: bunEnv,
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stdin: "ignore",
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stdout: "pipe",
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stderr: "pipe",
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timeout: 10_000,
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});
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const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
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expect(stdout).toBe("undefined undefined\n");
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expect(stderr).toBe("");
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expect(exitCode).toBe(0);
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});
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