Core_Upgrader::_auto_update_enabled_for_versions( string $ver_current, string $ver_offered, mixed $auto_update_core )

	public static function _auto_update_enabled_for_versions(
		$ver_current,
		$ver_offered,
		$auto_update_core
	) {
		// Parse the version strings.
		$current = self::parse_version_string( $ver_current );
		$offered = self::parse_version_string( $ver_offered );

		// Ensure they are valid.
		if ( ! $current || ! $offered ) {
			return false;
		}

		$failure_data = get_site_option( 'auto_core_update_failed' );
		if ( $failure_data ) {
			// If this was a critical update failure, cannot update.
			if ( ! empty( $failure_data['critical'] ) ) {
				return false;
			}

			// Don't claim we can update on update-core.php if we have a
			// non-critical failure logged.
			if (
				$ver_current == $failure_data['current'] &&
				false !== strpos( $ver_offered, '.1.next.minor' )
			) {
				return false;
			}

			// Cannot update if we're retrying the same A to B update that
			// caused a non-critical failure.  Some non-critical failures do
			// allow retries, like download_failed.  WP-3.7.1 => WP-3.7.2
			// resulted in files_not_writable, if we are still on WP-3.7.1 and
			// still trying to update to WP-3.7.2.
			if (
				empty( $failure_data['retry'] ) &&
				$ver_current == $failure_data['current'] &&
				$ver_offered == $failure_data['attempted']
			) {
				return false;
			}
		}

		// That concludes all the sanity checks, now we can do some work.

		// Default values for upgrade control flags.
		$upgrade_minor   = true;
		$upgrade_patch   = true;
		$upgrade_dev     = true;
		$upgrade_nightly = true;

		// Process the value from the WP_AUTO_UPDATE_CORE constant.
		if ( ! is_null( $auto_update_core ) ) {
			if ( false === $auto_update_core ) {
				// Disable automatic updates, unless a later filter allows it.
				$upgrade_minor   = false;
				$upgrade_patch   = false;
				$upgrade_dev     = false;
				$upgrade_nightly = false;
			} elseif ( 'patch' === $auto_update_core ) {
				// Only allow patch, nightly, or dev (pre-release) version
				// updates.  If you're running nightly builds, this is probably
				// not the setting you want, because you will still get new
				// minor versions.
				$upgrade_minor = false;
			}
			// Else: Default setting (true, 'minor', or any other unrecognized
			// value). Automatically update to new minor, patch, development
			// (pre-release), or nightly versions.
		}

		// 1.0.0-beta2+nightly.20181019 -> 1.0.0-beta2+nightly.20181020
		// We only need to confirm that the major version is the same and check
		// the nightly build date.
		if (
			$current['nightly'] &&
			$offered['nightly'] &&
			$current['nightly'] < $offered['nightly']
		) {
			/**
			 * Filters whether to enable automatic core updates for nightly
			 * releases.
			 *
			 * @since 1.0.0
			 *
			 * @param bool $upgrade_nightly Whether to enable automatic updates
			 *                              for nightly releases.
			 * @param array $current The array of parts of the current version.
			 * @param array $offered The array of parts of the offered version.
			 */
			$upgrade_nightly = apply_filters(
				'allow_nightly_auto_core_updates',
				$upgrade_nightly,
				$current,
				$offered
			);
			// If we're running the same major version as the proposed nightly,
			// then the above filter is all we need and we return its result.
			//
			// If the upgrade was denied via the WP_AUTO_UPDATE_CORE constant
			// or via this filter, return false.
			//
			// Otherwise, fall through to the 'allow_major_auto_core_updates'
			// filter below, because an auto-update to a nightly from a
			// different major version should be specifically approved.
			if ( $current['major'] === $offered['major'] ) {
				return $upgrade_nightly;
			} elseif ( ! $upgrade_nightly ) {
				return false;
			}

		} elseif ( $current['nightly'] || $offered['nightly'] ) {
			// Never auto-update from a nightly build to a non-nightly build,
			// or vice versa.
			return false;

		} elseif ( ! $current['prerelease'] && $offered['prerelease'] ) {
			// If not a nightly build, never auto-update from a release to a
			// pre-release version.
			return false;

		} elseif ( $offered['prerelease'] && (
			$current['major'] !== $offered['major'] ||
			$current['minor'] !== $offered['minor'] ||
			$current['patch'] !== $offered['patch']
		) ) {
			// If not a nightly build, never auto-update to a pre-release of a
			// different semver version.
			return false;
		}

		// Major version updates (1.2.3 -> 2.0.0, 1.2.3 -> 2.3.4).
		if ( $current['major'] > $offered['major'] ) {
			return false;
		} elseif ( $current['major'] < $offered['major'] ) {
			/**
			 * Filters whether to enable automatic core updates to a newer
			 * semver major release.
			 *
			 * @note Be careful with this filter! New major versions of
			 * ClassicPress may contain breaking changes.
			 * @see https://semver.org/
			 *
			 * @since WP-3.7.0
			 * @since 1.0.0 Version numbering scheme changed from WordPress
			 * to ClassicPress (semver). New parameters $current and $offered.
			 *
			 * @param bool $upgrade_major Whether to enable automatic updates
			 *                            to new major versions.
			 * @param array $current The array of parts of the current version.
			 * @param array $offered The array of parts of the offered version.
			 */
			return apply_filters(
				'allow_major_auto_core_updates',
				false,
				$current,
				$offered
			);
		}

		// Minor updates (1.1.3 -> 1.2.0).
		if ( $current['minor'] > $offered['minor'] ) {
			return false;
		} elseif ( $current['minor'] < $offered['minor'] ) {
			/**
			 * Filters whether to enable automatic core updates to a newer
			 * semver minor release.
			 *
			 * @since WP-3.7.0
			 * @since 1.0.0 Version numbering scheme changed from WordPress
			 * to ClassicPress (semver). New parameters $current and $offered.
			 *
			 * @param bool $upgrade_minor Whether to enable automatic updates
			 *                            to a newer semver minor release.
			 * @param array $current The array of parts of the current version.
			 * @param array $offered The array of parts of the offered version.
			 */
			return apply_filters(
				'allow_minor_auto_core_updates',
				$upgrade_minor,
				$current,
				$offered
			);
		}

		// Patch updates (1.0.0 -> 1.0.1 -> 1.0.2).
		if ( $current['patch'] < $offered['patch'] ) {
			/**
			 * Filters whether to enable automatic core updates to a newer
			 * semver patch release.
			 *
			 * @since 1.0.0
			 *
			 * @param bool $upgrade_patch Whether to enable automatic updates
			 *                            to a newer semver patch release.
			 * @param array $current The array of parts of the current version.
			 * @param array $offered The array of parts of the offered version.
			 */
			return apply_filters(
				'allow_patch_auto_core_updates',
				$upgrade_patch,
				$current,
				$offered
			);
		}

		// Prerelease versions (same semver version, several different cases).
		if (
			// Update from pre-release to release of the same version.
			( $current['prerelease'] && ! $offered['prerelease'] ) ||
			// Update from pre-release to a later pre-release of the same version.
			( $current['prerelease'] < $offered['prerelease'] )
		) {
			/**
			 * Filters whether to enable automatic core updates from prerelease
			 * versions.
			 *
			 * This filter is called if the current version is a pre-release,
			 * and the offered version is a newer pre-release of the same
			 * semver version, or the final release of the same semver version.
			 *
			 * @since WP-3.7.0
			 * @since 1.0.0 Version numbering scheme changed from WordPress
			 * to ClassicPress (semver). New parameters $current and $offered.
			 *
			 * @param bool $upgrade_dev Whether to enable automatic updates
			 *                          from prereleases.
			 * @param array $current The array of parts of the current version.
			 * @param array $offered The array of parts of the offered version.
			 */
			return apply_filters(
				'allow_dev_auto_core_updates',
				$upgrade_dev,
				$current,
				$offered
			);
		}

		// If we're still not sure, we don't want it.
		return false;
	}