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fix(types): ExecProcess streams are undefined, not null, when absent - #7847
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PedroRosalba wants to merge 1 commit into
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PedroRosalba wants to merge 1 commit into
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`ExecProcess.stdin`, `.stdout` and `.stderr` are `jsg::Optional` getters (`ExecProcess::getStdin/getStdout/getStderr`), and JSG wraps an empty `jsg::Optional` as `undefined`; only `kj::Maybe` becomes `null`. The hand-written `JSG_TS_OVERRIDE` declared all three as `X | null`, so `proc.stdout === null` never holds, and `if (proc.stderr !== null) proc.stderr.getReader()` compiles and throws when the stream was not provided. Absent is the common case: stdin unless `stdin: "pipe"` (or a PTY), stdout with `stdout: "ignore"`, stderr with `stderr: "ignore"` or `"combined"` (so also with a PTY). The Containers docs already describe the three fields as `| undefined`. Declare them optional (`readonly stdin?: WritableStream`, ...), which is what the generator emits for `jsg::Optional` properties elsewhere (`DurableObjectState.container?`, `ContainerSnapshot.name?`) and what the `DurableObjectStub.name?` override already does for a `jsg::Optional` getter. Types only; no runtime change. Verified on the built binary against a Docker container: in the default, `stdout: "ignore"` + `stderr: "ignore"`, `stderr: "combined"`, `stdin: "pipe"` and `pty: true` configurations every absent stream reads `typeof undefined` and `=== null` is false. Tests: //types:test/types/container (new; fails against the previous snapshot), //src/workerd/server/tests/container-client:container-client@ (existing runtime coverage; needs Docker). Precedent for an optional prototype getter in an override: Request.cf (jsg::Optional getCf, overridden as `readonly cf?: Cf` in http.h).
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Problem
ExecProcess(returned byctx.container.exec()) declaresreadonly stdin: WritableStream | null,readonly stdout: ReadableStream | null,readonly stderr: ReadableStream | null. The getters returnjsg::Optional<...>, and JSG wraps an emptyjsg::Optionalasundefined; onlykj::Maybebecomesnull. Absent is the common case:stdinunlessstdin: "pipe"(or a PTY),stdoutwithstdout: "ignore",stderrwithstderr: "ignore"or"combined"(so also with a PTY). As a resultproc.stdin === nullis never true, andif (proc.stdout !== null) proc.stdout.getReader()compiles and throwsTypeError: Cannot read properties of undefined.The Containers docs already say: "A stream that the process does not provide is undefined." and "The Workers TypeScript types declare stdin, stdout, and stderr as | null. Test for a stream, such as if (process.stderr), instead of comparing with null."
Fix
Declare the three as optional (
readonly stdin?: WritableStream, ...) in theJSG_TS_OVERRIDEinsrc/workerd/api/container.h, which is what the generator emits forjsg::Optionalproperties elsewhere (DurableObjectState.container?,ContainerSnapshot.name?) and whatRequest.cfdoes for ajsg::Optionalgetter in an override. Types only.Type-level breaking change: under
strictNullChecks,=== nullchecks on these fields become a compile error, which is the point: they were never true.Tests
bazel test //types:test/types/container(new; fails on the previous snapshot)//src/workerd/server/tests/container-client:container-client@(existing runtime coverage; needs Docker)stdout: "ignore"+stderr: "ignore",stderr: "combined",stdin: "pipe"andpty: trueconfigurations: every absent stream istypeof "undefined"and=== nullis false.just generate-typesreproduces the snapshot edits byte for byte.Tested on macOS (Apple Silicon) only.