fix: --yaml-stream produces correct output matching C++ jsonnet/go-jsonnet#1026
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The --yaml-stream (-y) CLI flag had four bugs:
1. Missing initial `---` document start marker
2. Missing `...` document end marker
3. Rendered each document as YAML instead of JSON
4. Did not error on non-array input (silently fell through to normal rendering)
Cross-implementation comparison for input `[{"a":1},{"b":2}]`:
| Feature | C++ jsonnet | go-jsonnet | sjsonnet (before) | sjsonnet (after) |
|----------------------|----------------|----------------|-------------------|------------------|
| Initial `---` | Yes | Yes | No | Yes |
| Trailing `...` | Yes | Yes | No | Yes |
| Document format | JSON | JSON | YAML | JSON |
| Non-array error | Yes | Yes | No (silent) | Yes |
| Empty array output | (empty) | (empty) | `\n` | (empty) |
Output is now byte-identical to C++ jsonnet for all tested cases.
Root cause: The YAML stream code in SjsonnetMainBase.scala used
`config.copy(yamlOut = true)` which forced YAML rendering instead of JSON,
had incorrect `---` prefix logic (only for scalars or non-first elements),
and fell through to `renderNormal` for non-array values instead of erroring.
Fix: Rewrite the YAML stream handler to:
- Write `---\n` before each document
- Render each document as JSON using the standard Renderer
- Write `...\n` after all documents
- Produce an error with the value's type name for non-array input
- Write directly to stdout stream to avoid double-newline from println
- Handle --output-file correctly for the YAML stream case
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Summary
This PR fixes
--yaml-stream(-y) output to match C++ jsonnet and go-jsonnet stream behavior.Before this PR, sjsonnet rendered the top-level array using YAML-style output without the JSON document stream markers expected by C++ jsonnet/go-jsonnet.
Behavior comparison
Local reference versions used:
v0.22.0v0.22.00.5.0-pre99[1, 2]with-y---\n1\n---\n2\n...\n[]with-y\n...\n{a: 1}with-yThe intentional compatibility target is C++ jsonnet/go-jsonnet. jrsonnet differs for empty arrays and error wording.
Changes
SjsonnetMainBase.scala: render YAML streams as JSON documents separated by---and terminated by..., with empty arrays producing no outputSjsonnetMainBase.scala: reject non-array top-level values in stream mode with the C++/go-jsonnet style errorMainTests.scala: update expected output and add non-array / empty-array regression coverageTests
rtk ./mill 'sjsonnet.jvm[3.3.7]'.test.testOnly sjsonnet.MainTests rtk git diff --check upstream/master...HEADBoth passed locally after rebasing onto
upstream/master.