Merge #3053

3053: Feature: downloading lsp server from GitHub r=matklad a=Veetaha

This is currently very WIP, I may need to change this and that, add "download language server command", logging stuff (for future bug reports), etc., but it already works.
Also didn't test this on windows yet and mac (don't have the latter)

The quirks:
* Downloaded binary doesn't have executable permissions by default, that's why we ~~`chmod 111`~~ (**[UPD]** `chmod 755` as per @lnicola [suggestion](https://github.com/rust-analyzer/rust-analyzer/pull/3053#discussion_r376694456)) for it.
* To remove installed binary run `rm /${HOME}/.config/Code/User/globalStorage/matklad.rust-analyzer/ra_lsp_server-linux`, ~~note that `-f` flag is necessary, because of `111` permissions (I think this should be changed)~~ (**[UPD]** --force is no longer needed due to 755 permissions).

I also tried to keep things simple and not to use too many dependencies, all the ones added have 0 dependencies, (`ts-not-nil` is my personal npm package, that imitates `unwrap()` in TypeScript)

**[UPD]** I reduced throttle latency of progress indicator to 200ms for smoother UX


// TODO:
- [x] ~~Add `Rust Analyzer: Download latest language server` vscode command.~~ **[UPD]**: having reviewed the code and estimated available options I concluded that this feature requires too many code changes, I'd like to extract this into a separate PR after we merge this one.
- [x] Add some logging for future debugging
- [x] ~~Gracefully handle the case when language server is not available (e.g. no internet connection, user explicitly rejected the download, etc.)~~ **[UPD]** Decided to postpone better implementation of graceful degradation logic as per [conversation](https://rust-lang.zulipchat.com/#narrow/stream/185405-t-compiler.2Fwg-rls-2.2E0/topic/Deployment.20and.20installation/near/187758550).

Demo (**[UPD]** this is a bit outdated, but still mainly reflects the feature):
![ra-github-release-download-mvp](https://user-images.githubusercontent.com/36276403/74077961-4f248a80-4a2d-11ea-962f-27c650fd6c4c.gif)

Related issue: #2988 #3007 

Co-authored-by: Veetaha <[email protected]>
Co-authored-by: Veetaha <[email protected]>

1 files changed, 11 insertions, 1 deletions

diff --git a/editors/code/src/ctx.ts b/editors/code/src/ctx.ts
index aa75943bf..70042a479 100644
--- a/editors/code/src/ctx.ts
+++ b/editors/code/src/ctx.ts
@@ -11,6 +11,9 @@ export class Ctx {
     // deal with it.
     //
     // Ideally, this should be replaced with async getter though.
+    // FIXME: this actually needs syncronization of some kind (check how
+    // vscode deals with `deactivate()` call when extension has some work scheduled
+    // on the event loop to get a better picture of what we can do here)
     client: lc.LanguageClient | null = null;
     private extCtx: vscode.ExtensionContext;
     private onDidRestartHooks: Array<(client: lc.LanguageClient) => void> = [];
@@ -26,7 +29,14 @@ export class Ctx {
             await old.stop();
         }
         this.client = null;
-        const client = createClient(this.config);
+        const client = await createClient(this.config);
+        if (!client) {
+            throw new Error(
+                "Rust Analyzer Language Server is not available. " +
+                "Please, ensure its [proper installation](https://github.com/rust-analyzer/rust-analyzer/tree/master/docs/user#vs-code)."
+            );
+        }
+
         this.pushCleanup(client.start());
         await client.onReady();