FinfoMimeTypeDetector: incomplete handing of INCONCLUSIVE_MIME_TYPES

[marc-mabe]

Bug Report

Q	A
BC Break	yes/no
Version	3.0.7

Summary

FinfoMimeTypeDetector has defined INCONCLUSIVE_MIME_TYPES which contains text/plain.
This will be used on detectMimeType and if the detected type in this list it falls back to detectMimeTypeFromPath.

On the other hand the local file adapter uses detectMimeTypeFromFile which does not check for INCONCLUSIVE_MIME_TYPES at all.

How to reproduce

1. Create a tsv file (tab separated values)

2. Use local file adapter mimeType() (which used FinfoMimeTypeDetector::detectMimeTypeFromFile)

3. you will get text/plain

4. Create the same tsv file in memory adapter

5. Use local file adapter mimeType() (which used FinfoMimeTypeDetector::detectMimeType)

6. you will get text/tab-separated-values

Idea how to fix

• INCONCLUSIVE_MIME_TYPES should be used in all cases a path exists and fall back to detectMimeTypeFromPath
• if fallback detectMimeTypeFromPath returns null use the previous detected mime type

Something like this:

    public function detectMimeType(string $path, $contents): ?string
    {
            $mimeType = is_string($contents)
                ? $this->detectMimeTypeFromBuffer($contents)
                : null;
    
            if ($mimeType !== null && ! in_array($mimeType, self::INCONCLUSIVE_MIME_TYPES)) {
                return $mimeType;
            }
    
            return $this->detectMimeTypeFromPath($path) ?: $mimeType;
    }

    public function detectMimeTypeFromFile(string $path): ?string
    {
        $mimeType = @$this->finfo->file($path) ?: null;

        if ($mimeType !== null && ! in_array($mimeType, self::INCONCLUSIVE_MIME_TYPES)) {
            return $mimeType;
        }

        return $this->detectMimeTypeFromPath($path) ?: $mimeType;
    }

[GuySartorelli]

Yup, this is causing us some grief as well. Specifically the lack of

if fallback detectMimeTypeFromPath returns null use the previous detected mime type

We're getting a valid text/plain from detectMimeTypeFromFile(), but then it falls back to detectMimeTypeFromPath() which returns null and results in an exception being thrown.

I've raised #1710 to handle that part of this issue.