fix: convert format parse errors from Internal Error to user-facing messages#1076
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fix: convert format parse errors from Internal Error to user-facing messages#1076He-Pin wants to merge 1 commit into
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Motivation:
Format string parsing errors (e.g. `std.format("%z", [1])`, `std.format("hello %", [])`)
were thrown as `java.lang.Exception` in `Format.scala`, which propagated up to the
`Interpreter` where they were caught as generic exceptions and wrapped as "Internal Error"
with a full Java stack trace. This produced confusing output compared to go-jsonnet and
jrsonnet, which emit clean one-line error messages.
Modification:
- Wrap `parseFormatCached` and `lowerParsedFormat` calls in `Format.format()` with
try/catch that converts `java.lang.Exception` to `Error.fail(msg, pos)`, producing
clean sjsonnet error messages with position info.
- `Error` exceptions (already-sjsonnet errors) are re-thrown unchanged.
Result:
Format errors now produce clean messages like:
`sjsonnet.Error: [std.format] Unrecognized conversion type: z`
instead of:
`sjsonnet.Error: [std.format] Internal Error`
`Caused by: java.lang.Exception: Unrecognized conversion type: z`
` at sjsonnet.Format$... (full Java stack trace)`
Cross-implementation comparison:
| Expression | sjsonnet (before) | sjsonnet (after) | go-jsonnet | jrsonnet |
|---|---|---|---|---|
| `std.format("%z", [1])` | Internal Error + Java trace | Unrecognized conversion type: z | Unrecognised conversion type: z | unrecognized conversion type: z |
| `std.format("hello %", [])` | Internal Error + Java trace | Truncated format code at end of string | Truncated format code. | truncated format code |
| `std.format("%(key", [1])` | Internal Error + Java trace | Unterminated ( in format spec | Truncated format code. | truncated format code |
| `std.format("%2$s", arr)` | Internal Error + Java trace | Unrecognized conversion type: $ | Unrecognised conversion type: $ | unrecognized conversion type: $ |
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Summary
java.lang.ExceptioninFormat.scala, which got caught by the generic exception handler inInterpreterand wrapped as"Internal Error"with a full Java stack traceparseFormatCachedandlowerParsedFormatcalls inFormat.format()with try/catch that convertsjava.lang.ExceptiontoError.fail(msg, pos), producing clean user-facing error messagesCross-implementation comparison
std.format("%z", [1])Internal Error+ Java stack traceUnrecognized conversion type: zUnrecognised conversion type: zunrecognized conversion type: zstd.format("hello %", [])Internal Error+ Java stack traceTruncated format code at end of stringTruncated format code.truncated format codestd.format("%(key", [1])Internal Error+ Java stack traceUnterminated ( in format specTruncated format code.truncated format code"%z" % [1](operator)Internal Error+ Java stack traceUnrecognized conversion type: zUnrecognised conversion type: zunrecognized conversion type: zTest plan
./mill 'sjsonnet.jvm[3.3.8]'.test— all 29 tests passerror.format_invalid_conversion.jsonnet— verifies clean error message for%zerror.format_truncated.jsonnet— verifies clean error message for trailing%format_error_messages.jsonnet— verifies format operations still work correctly%operator andstd.formatboth produce clean errors