Don't request inline hints repeatedly

editors/code/src/ctx.ts

@@ -62,20 +62,23 @@ export class Ctx {
         this.extCtx.subscriptions.push(d);
     }
 
-    async sendRequestWithRetry<R>(method: string, param: any): Promise<R> {
+    async sendRequestWithRetry<R>(method: string, param: any, token: vscode.CancellationToken): Promise<R> {
         await this.client.onReady();
-        const nRetries = 3;
+        for (const delay of [2, 4, 6, 8, 10, null]) {
-        for (let triesLeft = nRetries; ; triesLeft--) {
             try {
-                return await this.client.sendRequest(method, param);
+                return await this.client.sendRequest(method, param, token);
             } catch (e) {
-                if (e.code === lc.ErrorCodes.ContentModified && triesLeft > 0) {
+                if (e.code === lc.ErrorCodes.ContentModified && delay !== null) {
+                    await sleep(10 * (1 << delay))
                     continue;
                 }
                 throw e;
             }
         }
+        throw 'unreachable'
     }
 }
 
 export type Cmd = (...args: any[]) => any;
+
+const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms))

editors/code/src/inlay_hints.ts

@@ -41,6 +41,7 @@ const typeHintDecorationType = vscode.window.createTextEditorDecorationType({
 });
 
 class HintsUpdater {
+    private pending: Map<string, vscode.CancellationTokenSource> = new Map();
     private ctx: Ctx;
     private enabled = true;
 
@@ -67,7 +68,8 @@ class HintsUpdater {
 
     private async refreshEditor(editor: vscode.TextEditor): Promise<void> {
         const newHints = await this.queryHints(editor.document.uri.toString());
-        const newDecorations = (newHints ? newHints : []).map(hint => ({
+        if (newHints == null) return;
+        const newDecorations = newHints.map(hint => ({
             range: hint.range,
             renderOptions: {
                 after: {
@@ -98,9 +100,20 @@ class HintsUpdater {
         const request: InlayHintsParams = {
             textDocument: { uri: documentUri },
         };
-        return this.ctx.sendRequestWithRetry<InlayHint[] | null>(
+        let tokenSource = new vscode.CancellationTokenSource();
+        let prev = this.pending.get(documentUri);
+        if (prev) prev.cancel()
+        this.pending.set(documentUri, tokenSource);
+        try {
+            return await this.ctx.sendRequestWithRetry<InlayHint[] | null>(
                 'rust-analyzer/inlayHints',
                 request,
+                tokenSource.token,
             );
+        } finally {
+            if (!tokenSource.token.isCancellationRequested) {
+                this.pending.delete(documentUri)
+            }
+        }
     }
 }