Detect the first time a VS Code extension version is loaded - vscode-extensions

Question

I'd like to take an action the first time a user loads a new version of my VS Code extension. This is different from merely detecting first run as described by the How to run vscode extension command just right after installation? because I don't want to detect "just right after installation" I want to detect first run of each new version which is a totally different problem.
Mike Lischke's answer to that question doesn't actually answer that question, it answers this question, but that doesn't mean this is a duplicate question, it means the response to the other question doesn't actually answer the asked question, and since unlike many people I actually read the question, I didn't bother to read the answers, because answers to that question are not what I seek. Frankly I'm tempted to delete the question myself just to spite Stack Overflow because I'm fed up with this crap. Do whatever you like.
Searching the net turned up sample code
export function activate(context: vscode.ExtensionContext) {
if (context.firstTimeUse) {
//do the one-time-per-version-update thing
}
}
but ExtensionContext doesn't seem to have this property, at least not any more.
So how do you do it now?
I could record the version in a file and compare to the file before updating it, but if there's baked in support I'd rather do it the supported way.

Answer 1

There is no supported mechanism.
Since each update gets a new folder, you don't need to log a timestamp, just probe for the file. If it exists, not first run. If it doesn't exist, first run so create the file and do other first run things.
This is so simple and straightforward there probably won't ever be a supported mechanism. Thanks to Lex Li in the comments for confirming that this is the standard solution.
If you need to differentiate major, minor and maintenance releases, the simplest solution is to store the version string in context.globalState. You begin by trying to fetch from context.globalState. Absence means first run ever. If it's present, an exact match for current version means no change. For a non-match you can parse out major and minor version numbers context.globalState.
const currentVersion = context.extension.packageJSON.version as string;
const lastVersion = context.globalState.get("version") as string ?? "0.0.0"
if (lastVersion !== currentVersion) {
logger.warn(`Updated to ${currentVersion}`);
const lastVersionPart = lastVersion.split(".");
const currVersionPart = currentVersion.split(".");
if (lastVersionPart[0] !== currVersionPart[0]) {
// major version change
advertiseWalkthrough();
if (lastVersionPart[1] !== currVersionPart[1]) {
// minor version change
launchWhatsNew();
} else {
// it's a maintenance version change so don't pester the user
}
}
context.globalState.update("version", currentVersion);
}