swc-project / swc-project/plugins
Relay plugin causes sporadic errors
@kdy1 is already working on this.
Since Mar 21, 2026.
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Description
@kwonoj we've been having a lot of success using @swc/plugin-relay so far, but it seems to sporadically fail in our CI environment. I've updated @swc/core, @swc/jest and @swc/plugin-relay but am still experiencing issues. Without @swc/plugin-relay, the tests pass every time. With @swc/plugin-relay, our Jest tests can fail in two different ways:
- The Jest tests run to completion, but the final results are not logged and the process never exits, causing our CI build to timeout
- Some tests fail with the following stacktrace. In these cases, the process often does not exit (See # 1)
thread '<unnamed>' panicked at 'range end index 9725912 out of range for slice of length 4780000', library/core/src/slice/index.rs:73:5
stack backtrace:
0: 0x7fdafe40c6ad - <unknown>
1: 0x7fdafe43331c - <unknown>
2: 0x7fdafe408241 - <unknown>
3: 0x7fdafe40e045 - <unknown>
4: 0x7fdafe40dcb9 - <unknown>
5: 0x7fdafe40e5e2 - <unknown>
6: 0x7fdafe40e4c7 - <unknown>
7: 0x7fdafe40cb64 - <unknown>
8: 0x7fdafe40e1f9 - <unknown>
9: 0x7fdafcc97813 - <unknown>
10: 0x7fdafe434f76 - <unknown>
11: 0x7fdafe42b237 - <unknown>
12: 0x7fdafe430366 - <unknown>
13: 0x7fdafcc97926 - <unknown>
14: 0x7fdafd5cbab1 - <unknown>
15: 0x7fdafd5bc647 - <unknown>
16: 0x7fdafd598619 - <unknown>
17: 0x7fdafd51cd95 - <unknown>
18: 0x7fdafd5196bd - <unknown>
19: 0x7fdafd518da9 - <unknown>
20: 0x7fdafd4dfd25 - <unknown>
21: 0x7fdafd4c702f - <unknown>
22: 0x7fdafd1ddb58 - <unknown>
23: 0x7fdafd4ec444 - <unknown>
24: 0x7fdafd4e44f6 - <unknown>
25: 0x7fdafd4e7770 - <unknown>
26: 0x7fdafcf56cb8 - <unknown>
27: 0xaadf9d - _ZN6v8impl12_GLOBAL__N_123FunctionCallbackWrapper6InvokeERKN2v820FunctionCallbackInfoINS2_5ValueEEE
28: 0xd4a18e - _ZN2v88internal12_GLOBAL__N_119HandleApiCallHelperILb0EEENS0_11MaybeHandleINS0_6ObjectEEEPNS0_7IsolateENS0_6HandleINS0_10HeapObjectEEESA_NS8_INS0_20FunctionTemplateInfoEEENS8_IS4_EENS0_16BuiltinArgumentsE
29: 0xd4b5af - _ZN2v88internal21Builtin_HandleApiCallEiPmPNS0_7IsolateE
30: 0x15e7959 - Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_BuiltinExit
failed to handle: range end index 9725912 out of range for slice of length 4780000
Stack backtrace:
0: <unknown>
1: <unknown>
2: _ZN6v8impl12_GLOBAL__N_123FunctionCallbackWrapper6InvokeERKN2v820FunctionCallbackInfoINS2_5ValueEEE
3: _ZN2v88internal12_GLOBAL__N_119HandleApiCallHelperILb0EEENS0_11MaybeHandleINS0_6ObjectEEEPNS0_7IsolateENS0_6HandleINS0_10HeapObjectEEESA_NS8_INS0_20FunctionTemplateInfoEEENS8_IS4_EENS0_16BuiltinArgumentsE
4: _ZN2v88internal21Builtin_HandleApiCallEiPmPNS0_7IsolateE
5: Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_BuiltinExit
at Compiler.transformSync (node_modules/@swc/core/index.js:137:25)
at transformSync (node_modules/@swc/core/index.js:217:21)
at Object.process (node_modules/@swc/jest/index.js:71:45)
at ScriptTransformer.transformSource (node_modules/@jest/transform/build/ScriptTransformer.js:619:31)
at ScriptTransformer._transformAndBuildScript (node_modules/@jest/transform/build/ScriptTransformer.js:765:40)
at ScriptTransformer.transform (node_modules/@jest/transform/build/ScriptTransformer.js:822:19)
Unfortunately I can't recreate this locally so I can't provide a reproduction repo for you to see it in. Hopefully something in the stack trace stands out 😄. One note, the end index 9725912 is exactly the same in all cases of this error, while the slice length 4780000 can vary.
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