Refactored out detectFileMIMEType, matchesMIMEType logic for reuse. Added standalone isMIMEType validator for flexibility

[dapzthelegend]

Summary

Adds a new built-in mimetype validator for file paths.

It supports both exact MIME matches and wildcard subtype matches:

validate.Var("photo.png", "mimetype=image/png")
validate.Var("photo.png", "mimetype=image/*")

Changes

• add mimetype as a built-in validation tag
• extract shared file MIME detection logic
• refactor isImage to reuse the shared MIME detection helper
• keep isImage's existing explicit image MIME allowlist unchanged
• add docs and tests for mimetype
• add default translations and translation tests for mimetype

Notes

mimetype accepts:

• type/subtype
• type/*

Validation fails if the field is not a string, the file does not exist, the path is a directory, the MIME type cannot be detected, or the validator param is invalid.

Make sure that you've checked the boxes below before you submit PR:

• Tests exist or have been written that cover this particular change.

@go-playground/validator-maintainers

[dapzthelegend]

@the-fanan @zemzale

PR #1 to refactor out the mime detection logic and create a flexible standalone isMIMEType Validator

To keep existing behavior I've retained the type dict for isImage

[zemzale]

One small tests thing, but the code looks good.

Would like someone else opinion about the validator itself, before merging.

[zemzale]

suggestion: You don't need this. Since you do t.Tempdir all the files are going to be deleted when the testrun ends.

The directory is automatically removed when the test and all its subtests complete

source

[dapzthelegend]

Just reviewed this and updated it, thanks