TYPO3 Core

Addition: The error only occurs when including files prefixed with EXT: because the file then will be resolved relative on Line 462 of RessourceCompressor:

// build the file path relatively to the PATH_site
        if (strpos($filename, 'EXT:') === 0) {
            $file = GeneralUtility::getFileAbsFileName($filename);
        }

Including files with addJsFooterFile('/typo3conf/ext/myext/...') works perfectly.

It should be absolute here instead. Seems to be fixed when getting the absolute path after that:

// build the file path relatively to the PATH_site
        if (strpos($filename, 'EXT:') === 0) {
            $file = GeneralUtility::getFileAbsFileName($filename);
            $file = GeneralUtility::resolveBackPath(PATH_typo3 . $file);
        }

Patch set 2 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 3 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 4 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 5 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 6 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 7 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 8 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 9 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 10 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/56803

Patch set 2 for branch TYPO3_8-7 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/57386