fix(common): Support fallbackToMimetype without buffer#16013
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kamilmysliwiec merged 1 commit intoDec 5, 2025
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Allow FileTypeValidator to validate files saved on disk where no buffer is available. Use mimetype as a fallback when fallbackToMimetype=true and buffer is missing. Preserves existing behavior when fallbackToMimetype is not enabled.
Pull Request Test Coverage Report for Build 530d5789-20c6-4be9-8007-847427805075Details
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This CodeSandbox demonstrates that FileTypeValidator fails when using Multer's diskStorage, because uploaded files in this mode do not include a buffer. Even with fallbackToMimetype=true, the validator still expects a buffer internally, which causes validation to fail incorrectly. Reproduction: https://codesandbox.io/p/devbox/nest-filetypevalidator-pipe-lqt4wv This PR fixes the behavior by:
This resolves the inconsistency between the documented behavior and the actual validator behavior. |
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lgtm |
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Allow FileTypeValidator to validate files saved on disk where no buffer is available.
Use mimetype as a fallback when fallbackToMimetype=true and buffer is missing.
Preserves existing behavior when fallbackToMimetype is not enabled.
PR Checklist
Please check if your PR fulfills the following requirements:
PR Type
What kind of change does this PR introduce?
What is the current behavior?
When using Multer’s
diskStorage, uploaded files do not include abuffer.FileTypeValidatorrequires a buffer unlessskipMagicNumbersValidationis enabled.Even when
fallbackToMimetype=true, validation fails because thebufferis missing.This makes it impossible to validate disk-stored files using mimetype fallback.
Issue Number: N/A
What is the new behavior?
bufferis missing:fallbackToMimetype=true, validation usesmimetypeas a fallback.fallbackToMimetypeis not enabled, behavior remains unchanged (validation fails).This enables file validation for diskStorage without breaking existing logic.
Does this PR introduce a breaking change?
Other information
This change is backward-compatible and only affects cases where
fallbackToMimetypeis explicitly enabled. All existing behavior is preserved.