(fix) more robust mapping for Svelte diagnostics

Try to catch some cases of invalid ranges which may cause the LSP to get confused and not update diagnostics anymore
sveltejs#1019

Author: Simon Holthausen

packages/language-server/src/plugins/svelte/features/getDiagnostics.ts

@@ -1,9 +1,14 @@
 import { Warning } from 'svelte/types/compiler/interfaces';
 import { Diagnostic, DiagnosticSeverity, Position, Range } from 'vscode-languageserver';
-import { Document, isInTag, mapObjWithRangeToOriginal } from '../../../lib/documents';
+import {
+    Document,
+    isInTag,
+    mapObjWithRangeToOriginal,
+    TagInformation
+} from '../../../lib/documents';
 import { Logger } from '../../../logger';
 import { CompilerWarningsSettings } from '../../../ls-config';
-import { getLastPartOfPath } from '../../../utils';
+import { getLastPartOfPath, moveRangeStartToEndIfNecessary } from '../../../utils';
 import { SvelteDocument, TranspileErrorSource } from '../SvelteDocument';
 
 /**
@@ -56,6 +61,7 @@ async function tryGetDiagnostics(
                 };
             })
             .map((diag) => mapObjWithRangeToOriginal(transpiled, diag))
+            .map((diag) => adjustMappings(diag, document))
             .filter((diag) => isNoFalsePositive(diag, document));
     } catch (err) {
         return (await createParserErrorDiagnostic(err, document)).map((diag) =>
@@ -273,5 +279,35 @@ function isNoFalsePositive(diag: Diagnostic, doc: Document): boolean {
     return !hasExportedEnumWithThatName;
 }
 
+/**
+ * Some mappings might be invalid. Try to catch these cases here.
+ */
+function adjustMappings(diag: Diagnostic, doc: Document): Diagnostic {
+    if (diag.range.start.character < 0) {
+        diag.range.start.character = 0;
+    }
+    if (diag.range.end.character < 0) {
+        diag.range.end.character = 0;
+    }
+    if (diag.range.start.line < 0) {
+        diag.range.start = { line: 0, character: 0 };
+    }
+    if (diag.range.end.line < 0) {
+        diag.range.end = { line: 0, character: 0 };
+    }
+    diag.range = moveRangeStartToEndIfNecessary(diag.range);
+
+    if (
+        diag.code === 'css-unused-selector' &&
+        doc.styleInfo &&
+        !isInTag(diag.range.start, doc.styleInfo)
+    ) {
+        diag.range.start = (doc.styleInfo as TagInformation).startPos;
+        diag.range.end = diag.range.start;
+    }
+
+    return diag;
+}
+
 const scssNodeRuntimeHint =
     'If you use SCSS, it may be necessary to add the path to your NODE runtime to the setting `svelte.language-server.runtime`, or use `sass` instead of `node-sass`. ';

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

@@ -11,6 +11,7 @@ import { LSAndTSDocResolver } from '../LSAndTSDocResolver';
 import { convertRange, getDiagnosticTag, mapSeverity } from '../utils';
 import { SvelteDocumentSnapshot } from '../DocumentSnapshot';
 import { isInGeneratedCode } from './utils';
+import { swapRangeStartEndIfNecessary } from '../../../utils';
 
 export class DiagnosticsProviderImpl implements DiagnosticsProvider {
     constructor(private readonly lsAndTsDocResolver: LSAndTSDocResolver) {}
@@ -65,7 +66,7 @@ export class DiagnosticsProviderImpl implements DiagnosticsProvider {
             .filter(hasNoNegativeLines)
             .filter(isNoFalsePositive(document, tsDoc))
             .map(enhanceIfNecessary)
-            .map(swapRangeStartEndIfNecessary);
+            .map(swapDiagRangeStartEndIfNecessary);
     }
 
     private async getLSAndTSDoc(document: Document) {
@@ -190,16 +191,8 @@ function enhanceIfNecessary(diagnostic: Diagnostic): Diagnostic {
 /**
  * Due to source mapping, some ranges may be swapped: Start is end. Swap back in this case.
  */
-function swapRangeStartEndIfNecessary(diag: Diagnostic): Diagnostic {
-    if (
-        diag.range.end.line < diag.range.start.line ||
-        (diag.range.end.line === diag.range.start.line &&
-            diag.range.end.character < diag.range.start.character)
-    ) {
-        const start = diag.range.start;
-        diag.range.start = diag.range.end;
-        diag.range.end = start;
-    }
+function swapDiagRangeStartEndIfNecessary(diag: Diagnostic): Diagnostic {
+    diag.range = swapRangeStartEndIfNecessary(diag.range);
     return diag;
 }
 

packages/language-server/src/utils.ts

@@ -45,6 +45,29 @@ export function isInRange(range: Range, positionToTest: Position): boolean {
     );
 }
 
+export function isRangeStartAfterEnd(range: Range): boolean {
+    return (
+        range.end.line < range.start.line ||
+        (range.end.line === range.start.line && range.end.character < range.start.character)
+    );
+}
+
+export function swapRangeStartEndIfNecessary(range: Range): Range {
+    if (isRangeStartAfterEnd(range)) {
+        const start = range.start;
+        range.start = range.end;
+        range.end = start;
+    }
+    return range;
+}
+
+export function moveRangeStartToEndIfNecessary(range: Range): Range {
+    if (isRangeStartAfterEnd(range)) {
+        range.start = range.end;
+    }
+    return range;
+}
+
 export function isBeforeOrEqualToPosition(position: Position, positionToTest: Position): boolean {
     return (
         positionToTest.line < position.line ||