Implement switch/case completion prioritization

Co-authored-by: DanielRosenwasser <972891+DanielRosenwasser@users.noreply.github.com>

src/services/completions.ts

@@ -11,7 +11,8 @@ import {
     CancellationToken,
     canHaveDecorators,
     canUsePropertyAccess,
-    CaseBlock,
+    CaseBlock,
+    CaseClause,
     cast,
     CharacterCodes,
     ClassElement,
@@ -44,9 +45,10 @@ import {
     createSortedArray,
     createTextSpanFromBounds,
     createTextSpanFromNode,
-    createTextSpanFromRange,
-    Debug,
-    Declaration,
+    createTextSpanFromRange,
+    Debug,
+    Declaration,
+    DefaultClause,
     Decorator,
     Diagnostics,
     diagnosticToString,
@@ -349,12 +351,13 @@ import {
     skipAlias,
     SnippetKind,
     some,
-    SortedArray,
-    SourceFile,
-    SpreadAssignment,
-    startsWith,
-    stringToToken,
-    stripQuotes,
+    SortedArray,
+    SourceFile,
+    SpreadAssignment,
+    startsWith,
+    stringToToken,
+    stripQuotes,
+    SwitchStatement,
     Symbol,
     SymbolDisplay,
     SymbolDisplayPart,
@@ -1264,11 +1267,88 @@ function keywordFiltersFromSyntaxKind(keywordCompletion: TokenSyntaxKind): Keywo
     }
 }
 
-function getOptionalReplacementSpan(location: Node | undefined) {
-    // StringLiteralLike locations are handled separately in stringCompletions.ts
-    return location?.kind === SyntaxKind.Identifier ? createTextSpanFromNode(location) : undefined;
-}
-
+function getOptionalReplacementSpan(location: Node | undefined) {
+    // StringLiteralLike locations are handled separately in stringCompletions.ts
+    return location?.kind === SyntaxKind.Identifier ? createTextSpanFromNode(location) : undefined;
+}
+
+function shouldPrioritizeCaseAndDefaultKeywords(contextToken: Node | undefined, position: number): boolean {
+    if (!contextToken) return false;
+    
+    // Check if we're in a switch statement context
+    const switchStatement = findAncestor(contextToken, node => 
+        node.kind === SyntaxKind.SwitchStatement ? true :
+        isFunctionLikeDeclaration(node) || isClassLike(node) ? "quit" :
+        false
+    ) as SwitchStatement | undefined;
+    
+    if (!switchStatement) return false;
+    
+    const sourceFile = contextToken.getSourceFile();
+    const { line: currentLine, character: currentColumn } = getLineAndCharacterOfPosition(sourceFile, position);
+    
+    // Case 1: Cursor is directly inside the switch block
+    // switch (thing) {
+    //     /*cursor*/
+    // }
+    if (contextToken.parent === switchStatement.caseBlock) {
+        return true;
+    }
+    
+    // Case 2: Cursor is at the same column as a case/default keyword but on a different line,
+    // with at least one statement in the previous clause that meets certain conditions
+    const caseBlock = switchStatement.caseBlock;
+    if (!caseBlock) return false;
+    
+    // Find the last case/default clause before the cursor position
+    let lastClause: CaseClause | DefaultClause | undefined;
+    for (const clause of caseBlock.clauses) {
+        if (clause.pos >= position) break;
+        lastClause = clause;
+    }
+    
+    if (!lastClause) return false;
+    
+    // Check if cursor is at the same column as the last clause's keyword
+    const clauseKeywordPos = lastClause.kind === SyntaxKind.CaseClause ? 
+        lastClause.getFirstToken(sourceFile)!.getStart(sourceFile) :
+        lastClause.getFirstToken(sourceFile)!.getStart(sourceFile);
+    const { line: clauseLine, character: clauseColumn } = getLineAndCharacterOfPosition(sourceFile, clauseKeywordPos);
+    
+    if (currentLine === clauseLine || currentColumn !== clauseColumn) {
+        return false;
+    }
+    
+    // Check if there's at least one statement in the clause
+    if (!lastClause.statements || lastClause.statements.length === 0) {
+        return false;
+    }
+    
+    const lastStatement = lastClause.statements[lastClause.statements.length - 1];
+    
+    // Get position of the last statement
+    const { line: stmtLine, character: stmtColumn } = getLineAndCharacterOfPosition(sourceFile, lastStatement.getStart(sourceFile));
+    
+    // Check if it's a jump statement
+    const isJumpStatement = isBreakOrContinueStatement(lastStatement) ||
+                           lastStatement.kind === SyntaxKind.ReturnStatement ||
+                           lastStatement.kind === SyntaxKind.ThrowStatement;
+    
+    if (isJumpStatement) {
+        // For jump statements: prioritize if on same line as case, or on different line with different indentation
+        if (stmtLine === clauseLine || (stmtLine !== clauseLine && stmtColumn !== clauseColumn)) {
+            return true;
+        }
+    } else {
+        // For non-jump statements: prioritize only if on different line and different column  
+        if (stmtLine !== clauseLine && stmtColumn !== clauseColumn) {
+            return true;
+        }
+    }
+    
+    return false;
+}
+
 function completionInfoFromData(
     sourceFile: SourceFile,
     host: LanguageServiceHost,
@@ -1368,17 +1448,22 @@ function completionInfoFromData(
         includeSymbol,
     );
 
-    if (keywordFilters !== KeywordCompletionFilters.None) {
-        for (const keywordEntry of getKeywordCompletions(keywordFilters, !insideJsDocTagTypeExpression && isSourceFileJS(sourceFile))) {
-            if (
-                isTypeOnlyLocation && isTypeKeyword(stringToToken(keywordEntry.name)!) ||
-                !isTypeOnlyLocation && isContextualKeywordInAutoImportableExpressionSpace(keywordEntry.name) ||
-                !uniqueNames.has(keywordEntry.name)
-            ) {
-                uniqueNames.add(keywordEntry.name);
-                insertSorted(entries, keywordEntry, compareCompletionEntries, /*equalityComparer*/ undefined, /*allowDuplicates*/ true);
-            }
-        }
+    if (keywordFilters !== KeywordCompletionFilters.None) {
+        const shouldPrioritizeCaseDefault = shouldPrioritizeCaseAndDefaultKeywords(contextToken, position);
+        for (const keywordEntry of getKeywordCompletions(keywordFilters, !insideJsDocTagTypeExpression && isSourceFileJS(sourceFile))) {
+            if (
+                isTypeOnlyLocation && isTypeKeyword(stringToToken(keywordEntry.name)!) ||
+                !isTypeOnlyLocation && isContextualKeywordInAutoImportableExpressionSpace(keywordEntry.name) ||
+                !uniqueNames.has(keywordEntry.name)
+            ) {
+                uniqueNames.add(keywordEntry.name);
+                // Create a modified keyword entry with prioritized sort text for case/default in switch contexts
+                const modifiedKeywordEntry = shouldPrioritizeCaseDefault && (keywordEntry.name === "case" || keywordEntry.name === "default") 
+                    ? { ...keywordEntry, sortText: SortText.LocalDeclarationPriority }
+                    : keywordEntry;
+                insertSorted(entries, modifiedKeywordEntry, compareCompletionEntries, /*equalityComparer*/ undefined, /*allowDuplicates*/ true);
+            }
+        }
     }
 
     for (const keywordEntry of getContextualKeywords(contextToken, position)) {
@@ -4812,23 +4897,23 @@ function getCompletionData(
         return undefined;
     }
 
-    function tryGetFunctionLikeBodyCompletionContainer(contextToken: Node): FunctionLikeDeclaration | undefined {
-        if (contextToken) {
-            let prev: Node;
-            const container = findAncestor(contextToken.parent, (node: Node) => {
-                if (isClassLike(node)) {
-                    return "quit";
-                }
-                if (isFunctionLikeDeclaration(node) && prev === node.body) {
-                    return true;
-                }
-                prev = node;
-                return false;
-            });
-            return container && container as FunctionLikeDeclaration;
-        }
-    }
-
+    function tryGetFunctionLikeBodyCompletionContainer(contextToken: Node): FunctionLikeDeclaration | undefined {
+        if (contextToken) {
+            let prev: Node;
+            const container = findAncestor(contextToken.parent, (node: Node) => {
+                if (isClassLike(node)) {
+                    return "quit";
+                }
+                if (isFunctionLikeDeclaration(node) && prev === node.body) {
+                    return true;
+                }
+                prev = node;
+                return false;
+            });
+            return container && container as FunctionLikeDeclaration;
+        }
+    }
+
     function tryGetContainingJsxElement(contextToken: Node): JsxOpeningLikeElement | undefined {
         if (contextToken) {
             const parent = contextToken.parent;

tests/cases/fourslash/switchCaseCompletionPriority.ts

@@ -0,0 +1,125 @@
+/// <reference path="fourslash.ts" />
+
+//// declare const thing: string;
+
+//// // Basic switch block - should prioritize case/default
+//// switch (thing) {
+////     /*basic*/
+//// }
+
+//// // Same - show all completions (not at switch body level)
+//// switch (thing) {
+////   case 42:
+////   /*sameAll1*/
+//// }
+
+//// // Same - show all completions (after break at same column as case)
+//// switch (thing) {
+////   case 42:
+////   break;
+////   /*sameAll2*/
+//// }
+
+//// // Same - show all completions (complex nested structure)
+//// switch (thing) {
+////   case 42:
+////   if (Math.random()) {
+////   }
+////   else {
+////   }
+////   /*sameAll3*/
+//// }
+
+//// // NEW - prioritize case/default (after break on different column)
+//// switch (thing) {
+////   case 42:
+////     break;
+////   /*newPrio1*/
+//// }
+
+//// // NEW - prioritize case/default (break on same line)
+//// switch (thing) {
+////   case 42: break;
+////   /*newPrio2*/
+//// }
+
+//// // NEW - prioritize case/default (after return)
+//// switch (thing) {
+////   case 42:
+////     return 1;
+////   /*newPrio3*/
+//// }
+
+//// // NEW - prioritize case/default (after throw)
+//// switch (thing) {
+////   case 42:
+////     throw new Error();
+////   /*newPrio4*/
+//// }
+
+verify.completions(
+    {
+        marker: "basic",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.LocalDeclarationPriority },
+            { name: "default", sortText: completion.SortText.LocalDeclarationPriority }
+        ]
+    },
+    {
+        marker: "sameAll1",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.GlobalsOrKeywords },
+            { name: "default", sortText: completion.SortText.GlobalsOrKeywords }
+        ]
+    },
+    {
+        marker: "sameAll2",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.GlobalsOrKeywords },
+            { name: "default", sortText: completion.SortText.GlobalsOrKeywords }
+        ]
+    },
+    {
+        marker: "sameAll3",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.GlobalsOrKeywords },
+            { name: "default", sortText: completion.SortText.GlobalsOrKeywords }
+        ]
+    },
+    {
+        marker: "newPrio1",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.LocalDeclarationPriority },
+            { name: "default", sortText: completion.SortText.LocalDeclarationPriority }
+        ]
+    },
+    {
+        marker: "newPrio2",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.LocalDeclarationPriority },
+            { name: "default", sortText: completion.SortText.LocalDeclarationPriority }
+        ]
+    },
+    {
+        marker: "newPrio3",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.LocalDeclarationPriority },
+            { name: "default", sortText: completion.SortText.LocalDeclarationPriority }
+        ]
+    },
+    {
+        marker: "newPrio4",
+        isNewIdentifierLocation: false,
+        includes: [
+            { name: "case", sortText: completion.SortText.LocalDeclarationPriority },
+            { name: "default", sortText: completion.SortText.LocalDeclarationPriority }
+        ]
+    }
+);