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Blob/File type: preserve user-supplied MIME verbatim (WHATWG File API) #29258

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Blob: also fix S3File type canonicalization and slice flag

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Blob/File type: preserve user-supplied MIME verbatim (WHATWG File API) #29258

Blob: also fix S3File type canonicalization and slice flag
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Claude / Claude Code Review completed Apr 13, 2026 in 24m 2s

Code review found 1 important issue

Found 5 candidates, confirmed 5. See review comments for details.

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Severity Count
🔴 Important 1
🟡 Nit 0
🟣 Pre-existing 0
Severity File:Line Issue
🔴 Important src/bun.js/webcore/Blob.zig:2854-2866 getSliceFrom: content_type_was_set uses wrong length check, causing false positives

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Check failure on line 2866 in src/bun.js/webcore/Blob.zig

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@claude claude / Claude Code Review

getSliceFrom: content_type_was_set uses wrong length check, causing false positives 

In getSliceFrom (Blob.zig:2863), the PR replaces content_type_was_allocated with blob.content_type.len > 0 in the content_type_was_set formula, but blob.content_type at that point may already hold the inherited parent type (not a user-supplied value), causing the slice to be incorrectly marked as having a user-set content type. The correct operand is the content_type parameter (zero-length when the user passed no type), not the blob field after inheritance: use this.content_type_was_set or conte
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