Fix unused false positives (#377)

* (fix) Swallow unused false positives

`svelte2tsx` now also returns `exportedNames` through which we can easily get the props.
#277

Author: dummdidumm

packages/language-server/src/plugins/typescript/DocumentSnapshot.ts

@@ -1,5 +1,5 @@
 import { RawSourceMap, SourceMapConsumer } from 'source-map';
-import svelte2tsx from 'svelte2tsx';
+import svelte2tsx, { IExportedNames } from 'svelte2tsx';
 import ts from 'typescript';
 import { Position, Range } from 'vscode-languageserver';
 import {
@@ -82,17 +82,22 @@ export namespace DocumentSnapshot {
      * @param options options that apply to the svelte document
      */
     export function fromDocument(document: Document, options: SvelteSnapshotOptions) {
-        const { tsxMap, text, parserError, nrPrependedLines, scriptKind } = preprocessSvelteFile(
-            document,
-            options,
-        );
+        const {
+            tsxMap,
+            text,
+            exportedNames,
+            parserError,
+            nrPrependedLines,
+            scriptKind,
+        } = preprocessSvelteFile(document, options);
 
         return new SvelteDocumentSnapshot(
             document,
             parserError,
             scriptKind,
             text,
             nrPrependedLines,
+            exportedNames,
             tsxMap,
         );
     }
@@ -121,6 +126,7 @@ function preprocessSvelteFile(document: Document, options: SvelteSnapshotOptions
     let parserError: ParserError | null = null;
     let nrPrependedLines = 0;
     let text = document.getText();
+    let exportedNames: IExportedNames = { has: () => false };
 
     const scriptKind = [
         getScriptKindFromAttributes(document.scriptInfo?.attributes ?? {}),
@@ -137,6 +143,7 @@ function preprocessSvelteFile(document: Document, options: SvelteSnapshotOptions
         });
         text = tsx.code;
         tsxMap = tsx.map;
+        exportedNames = tsx.exportedNames;
         if (tsxMap) {
             tsxMap.sources = [document.uri];
 
@@ -164,7 +171,7 @@ function preprocessSvelteFile(document: Document, options: SvelteSnapshotOptions
         text = document.scriptInfo ? document.scriptInfo.content : '';
     }
 
-    return { tsxMap, text, parserError, nrPrependedLines, scriptKind };
+    return { tsxMap, text, exportedNames, parserError, nrPrependedLines, scriptKind };
 }
 
 /**
@@ -181,6 +188,7 @@ export class SvelteDocumentSnapshot implements DocumentSnapshot {
         public readonly scriptKind: ts.ScriptKind,
         private readonly text: string,
         private readonly nrPrependedLines: number,
+        private readonly exportedNames: IExportedNames,
         private readonly tsxMap?: RawSourceMap,
     ) {}
 
@@ -204,6 +212,10 @@ export class SvelteDocumentSnapshot implements DocumentSnapshot {
         return positionAt(offset, this.text);
     }
 
+    hasProp(name: string): boolean {
+        return this.exportedNames.has(name);
+    }
+
     async getFragment() {
         if (!this.fragment) {
             const uri = pathToUrl(this.filePath);

packages/language-server/src/plugins/typescript/features/DiagnosticsProvider.ts

@@ -4,6 +4,7 @@ import { Document, mapDiagnosticToOriginal, getTextInRange } from '../../../lib/
 import { DiagnosticsProvider } from '../../interfaces';
 import { LSAndTSDocResolver } from '../LSAndTSDocResolver';
 import { convertRange, mapSeverity } from '../utils';
+import { SvelteDocumentSnapshot } from '../DocumentSnapshot';
 
 export class DiagnosticsProviderImpl implements DiagnosticsProvider {
     constructor(private readonly lsAndTsDocResolver: LSAndTSDocResolver) {}
@@ -43,7 +44,7 @@ export class DiagnosticsProviderImpl implements DiagnosticsProvider {
             }))
             .map((diagnostic) => mapDiagnosticToOriginal(fragment, diagnostic))
             .filter(hasNoNegativeLines)
-            .filter(isNoFalsePositive(document.getText()));
+            .filter(isNoFalsePositive(document.getText(), tsDoc));
     }
 
     private getLSAndTSDoc(document: Document) {
@@ -60,12 +61,12 @@ function hasNoNegativeLines(diagnostic: Diagnostic): boolean {
     return diagnostic.range.start.line >= 0 && diagnostic.range.end.line >= 0;
 }
 
-function isNoFalsePositive(text: string) {
+function isNoFalsePositive(text: string, tsDoc: SvelteDocumentSnapshot) {
     return (diagnostic: Diagnostic) => {
         return (
             isNoJsxCannotHaveMultipleAttrsError(diagnostic) &&
             isNoUnusedLabelWarningForReactiveStatement(diagnostic) &&
-            isNoUsedBeforeAssigned(diagnostic, text)
+            isNoUsedBeforeAssigned(diagnostic, text, tsDoc)
         );
     };
 }
@@ -75,13 +76,16 @@ function isNoFalsePositive(text: string) {
  * without assigning a value in strict mode. Should not throw an error here
  * but on the component-user-side ("you did not set a required prop").
  */
-function isNoUsedBeforeAssigned(diagnostic: Diagnostic, text: string): boolean {
+function isNoUsedBeforeAssigned(
+    diagnostic: Diagnostic,
+    text: string,
+    tsDoc: SvelteDocumentSnapshot,
+): boolean {
     if (diagnostic.code !== 2454) {
         return true;
     }
 
-    const exportLetRegex = new RegExp(`export\\s+let\\s+${getTextInRange(diagnostic.range, text)}`);
-    return !exportLetRegex.test(text);
+    return !tsDoc.hasProp(getTextInRange(diagnostic.range, text));
 }
 
 /**

packages/language-server/test/plugins/typescript/testfiles/diagnostics-falsepositives.svelte

@@ -1,8 +1,9 @@
 <script lang="typescript">
-export let noUsedBeforeDeclare: number;
+export let noUsedBeforeDeclare: number, anotherUsed: boolean;
 const blubb = 2;
 $: bla = blubb * 2;
 </script>
 <p on:click on:click></p>
 {bla}
-{noUsedBeforeDeclare}
+{noUsedBeforeDeclare}
+{anotherUsed}

packages/svelte2tsx/index.d.ts

@@ -1,6 +1,11 @@
-type SvelteCompiledToTsx = {
-    code: string,
-    map: import("magic-string").SourceMap
+export interface SvelteCompiledToTsx {
+    code: string;
+    map: import("magic-string").SourceMap;
+    exportedNames: IExportedNames;
+}
+
+export interface IExportedNames {
+    has(name: string): boolean;
 }
 
 export default function svelte2tsx(

packages/svelte2tsx/src/nodes/ExportedNames.ts

@@ -1,11 +1,18 @@
-export class ExportedNames extends Map<
-    string,
-    {
-        type?: string;
-        identifierText?: string;
-        required?: boolean;
-    }
-> {
+// eslint-disable-next-line @typescript-eslint/interface-name-prefix
+export interface IExportedNames {
+    has(name: string): boolean;
+}
+
+export class ExportedNames
+    extends Map<
+        string,
+        {
+            type?: string;
+            identifierText?: string;
+            required?: boolean;
+        }
+    >
+    implements IExportedNames {
     /**
      * Creates a string from the collected props
      *

packages/svelte2tsx/src/svelte2tsx.ts

@@ -1039,5 +1039,6 @@ export function svelte2tsx(
     return {
         code: str.toString(),
         map: str.generateMap({ hires: true, source: options?.filename }),
+        exportedNames
     };
 }