Enum DowngradePolicy 

#[non_exhaustive]
pub enum DowngradePolicy {
    KeepProfile,
    ResetProfile,
}

What to do with the profile on disk when a newer Chromium milestone than the one this binary embeds last used it: the application was rolled back to a release on an older CEF.

Defaults to DowngradePolicy::KeepProfile.

What a rollback does to the profile

Chromium migrates its profile forward only, and Chrome calls a launch on a profile from a higher milestone an unsupported downgrade (chrome/browser/downgrade/). In practice a rollback to the previous milestone usually just works; what can go wrong is bounded by the stores whose format changed in between. A SQLite database whose schema is newer than the older Chromium can read — cookies, autofill, history — is left on disk and unused, so cookies stop persisting until the application is upgraded again, and for some of them Chromium shows its own “profile is from a newer version” dialog; an IndexedDB store whose data format is newer may be discarded as corrupt.

Chrome keeps a Last Version breadcrumb in its user data directory to recognize a downgrade. CEF does not write it, so the runtime does, in Cef::root_cache_path, and applies this policy when the breadcrumb names a higher milestone. A downgrade within a milestone, 152.0.7977.83 to 152.0.7977.50, is left alone either way, as Chrome leaves it, and a profile another running instance of the application holds is never touched.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

KeepProfile

Keep the profile and let Chromium open it, logging a warning that names both versions.

Nothing is deleted: whatever the older Chromium cannot read stays on disk and is back once the application is upgraded again. This is what Chrome does for a downgrade nobody administered.

ResetProfile

Move the root cache path aside and start on an empty profile, deleting the old one in the background.

The application starts as if freshly installed, on every platform and whatever changed between the two versions: cookies and sessions, local storage, IndexedDB, caches and granted permissions are gone, and a warning naming both versions is logged. For an application whose state lives on a server, or that would rather have every user start clean than some run on a half-readable profile.

Trait Implementations

impl Clone for DowngradePolicy

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for DowngradePolicy

impl Debug for DowngradePolicy

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for DowngradePolicy

fn default() -> Self

Returns the “default value” for a type.

impl Eq for DowngradePolicy

impl PartialEq for DowngradePolicy

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for DowngradePolicy