Phase 3 of plans/exit.md: the streaming-interface change, the load-bearing
piece for #341 (DSL exit statement) and #440 (strict mode).
- RecordTransformer.Transform and RecordTransformerFunc now return error.
All 69 Transform implementations and their dispatch helpers updated
(mechanical rewrite, compiler- and errcheck-verified).
- runSingleTransformerBatch, on a Transform error, forwards any output
produced before the failure plus an end-of-stream marker downstream, so
the rest of the chain and the record-writer drain and finish cleanly;
runSingleTransformer then surfaces the error to stream.Stream's select
loop (non-blocking send; first error wins) and signals upstream-done so
the record-reader stops. This is exactly the flush-then-exit sequencing a
future DSL 'exit N' needs.
- dataProcessingErrorChannel and FileOutputHandler.recordErroredChannel are
now chan error instead of chan bool; ChannelWriter still prints write-
error details at the site and sends the 'exiting due to data error'
sentinel, preserving the exact stderr shape pinned by regression cases.
- Mid-stream os.Exit sites converted to returned errors: put/filter DSL
begin/main/end-block errors and the non-boolean filter-expression case,
tee write/close failures, split write/open/close failures, join left-file
ingest failures (both half-streaming and sorted paths, with full error
plumbing through JoinBucketKeeper), histogram/stats2 ingest errors, surv
fit errors, and step stepper allocation (tStepperAllocator now returns
(tStepper, error); bad EWMA coefficients propagate; negative slwin
parameters are reported by the CLI parser via the existing
bad-stepper-name pattern).
- The two genuinely internal join-bucket-keeper states now use
lib.InternalCodingErrorWithMessageIf instead of hand-rolled print+exit.
- pkg/transformers is now os.Exit-free.
Behavior notes: the non-boolean filter message gains the standard 'mlr: '
prefix and a newline (it previously printed with neither); tee errors now
include the underlying cause. All 4779 regression cases pass unchanged;
mlr head early-out latency is unaffected (0.02s over 50M records).
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Logic for transforming input records into output records as requested by the user (sort, filter, etc.).:
The IRecordTransformer abstract record-transformer interface datatype, as well as the ChainTransformer Go-channel chaining mechanism for piping one transformer into the next.
The transformer lookup table, used for Miller command-line parsing, verb construction, and online help.
All the concrete record-transformers such as cat, tac, sort, put, and so on.
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