Fix panic in textDocument/completion when cached symbols cannot be rehydrated

internal/fourslash/tests/completionNullExportCondition_test.go

@@ -0,0 +1,69 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/core"
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	. "github.com/microsoft/typescript-go/internal/fourslash/tests/util"
+	"github.com/microsoft/typescript-go/internal/ls"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+// Regression test for panic when rehydrating cached export info fails.
+// This can happen when:
+// - Module resolution changes (e.g., null export conditions)
+// - Symbols are removed/renamed in a module
+// - Modules become unavailable
+// The language service should handle this gracefully instead of panicking.
+func TestCompletionNullExportCondition(t *testing.T) {
+	t.Parallel()
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+	const content = `// @module: esnext
+// @moduleResolution: node16
+// @allowJs: true
+// @noTypesAndSymbols: true
+// @noEmit: true
+
+// @Filename: /node_modules/dep/package.json
+{
+  "name": "dep",
+  "version": "1.0.0",
+  "exports": {
+    ".": {
+        "import": null,
+        "require": "./dist/index.js",
+        "types": "./dist/index.d.ts"
+    }
+  }
+}
+
+// @Filename: /node_modules/dep/dist/index.d.ts
+export const sourceMapsEnabled = true;
+export const someOtherExport = "value";
+
+// @Filename: /node_modules/dep/dist/index.mjs
+export const sourceMapsEnabled = true;
+export const someOtherExport = "value";
+
+// @Filename: /index.mts
+// Trigger auto-import completion - should work without panicking
+source/**/
+`
+	f := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	// This should not panic when requesting completions
+	f.VerifyCompletions(t, "", &fourslash.CompletionsExpectedList{
+		UserPreferences: &ls.UserPreferences{
+			IncludeCompletionsForModuleExports:    core.TSTrue,
+			IncludeCompletionsForImportStatements: core.TSTrue,
+		},
+		IsIncomplete: false,
+		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
+			CommitCharacters: &DefaultCommitCharacters,
+			EditRange:        Ignored,
+		},
+		Items: &fourslash.CompletionsExpectedItems{
+			// The exact items don't matter - we're just testing it doesn't panic
+		},
+	})
+}

internal/ls/autoimports.go

@@ -91,7 +91,9 @@ func (e *exportInfoMap) get(importingFile tspath.Path, ch *checker.Checker, key
 	if e.usableByFileName != importingFile {
 		return nil
 	}
-	return core.Map(e.exportInfo.Get(key), func(info CachedSymbolExportInfo) *SymbolExportInfo { return e.rehydrateCachedInfo(ch, info) })
+	return core.MapFiltered(e.exportInfo.Get(key), func(info CachedSymbolExportInfo) (*SymbolExportInfo, bool) {
+		return e.rehydrateCachedInfo(ch, info)
+	})
 }
 
 func (e *exportInfoMap) add(
@@ -227,12 +229,20 @@ func (e *exportInfoMap) search(
 			symbolName = info[0].capitalizedSymbolName
 		}
 		if matches(symbolName, info[0].targetFlags) {
-			rehydrated := core.Map(info, func(info CachedSymbolExportInfo) *SymbolExportInfo {
-				return e.rehydrateCachedInfo(ch, info)
-			})
-			filtered := core.FilterIndex(rehydrated, func(r *SymbolExportInfo, i int, _ []*SymbolExportInfo) bool {
-				return e.isNotShadowedByDeeperNodeModulesPackage(r, info[i].packageName)
-			})
+			// Rehydrate and filter in one pass to maintain correspondence between cached and rehydrated info
+			var rehydrated []*SymbolExportInfo
+			for i, cachedInfo := range info {
+				rehydratedInfo, ok := e.rehydrateCachedInfo(ch, cachedInfo)
+				if !ok {
+					// Symbol or module is no longer available, skip it
+					continue
+				}
+				if !e.isNotShadowedByDeeperNodeModulesPackage(rehydratedInfo, info[i].packageName) {
+					continue
+				}
+				rehydrated = append(rehydrated, rehydratedInfo)
+			}
+			filtered := rehydrated
 			if len(filtered) > 0 {
 				if res := action(filtered, symbolName, ambientModuleName != "", key); res != nil {
 					return res
@@ -254,7 +264,10 @@ func (e *exportInfoMap) isNotShadowedByDeeperNodeModulesPackage(info *SymbolExpo
 	return !ok || strings.HasPrefix(info.moduleFileName, packageDeepestNodeModulesPath)
 }
 
-func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymbolExportInfo) *SymbolExportInfo {
+// rehydrateCachedInfo attempts to restore a SymbolExportInfo from cached data.
+// Returns (info, true) if successful, or (nil, false) if the symbol or module
+// can no longer be found (e.g., due to module resolution changes or removed exports).
+func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymbolExportInfo) (*SymbolExportInfo, bool) {
 	if info.symbol != nil && info.moduleSymbol != nil {
 		return &SymbolExportInfo{
 			symbol:            info.symbol,
@@ -263,7 +276,7 @@ func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymb
 			exportKind:        info.exportKind,
 			targetFlags:       info.targetFlags,
 			isFromPackageJson: info.isFromPackageJson,
-		}
+		}, true
 	}
 	cached := e.symbols[info.id]
 	cachedSymbol, cachedModuleSymbol := cached.symbol, cached.moduleSymbol
@@ -275,7 +288,7 @@ func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymb
 			exportKind:        info.exportKind,
 			targetFlags:       info.targetFlags,
 			isFromPackageJson: info.isFromPackageJson,
-		}
+		}, true
 	}
 
 	moduleSymbol := core.Coalesce(info.moduleSymbol, cachedModuleSymbol)
@@ -287,7 +300,9 @@ func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymb
 		}
 	}
 	if moduleSymbol == nil {
-		panic(fmt.Sprintf("Could not find module symbol for %s in exportInfoMap", info.moduleName))
+		// Module is no longer available - this can happen when module resolution changes
+		// or the module is removed. Just skip this cached entry.
+		return nil, false
 	}
 	symbol := core.Coalesce(info.symbol, cachedSymbol)
 	if symbol == nil {
@@ -299,7 +314,9 @@ func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymb
 	}
 
 	if symbol == nil {
-		panic(fmt.Sprintf("Could not find symbol '%s' by key '%s' in module %s", info.symbolName, info.symbolTableKey, moduleSymbol.Name))
+		// Symbol is no longer available in the module - this can happen when exports change
+		// or the symbol is removed/renamed. Just skip this cached entry.
+		return nil, false
 	}
 	e.symbols[info.id] = symbolExportEntry{symbol, moduleSymbol}
 	return &SymbolExportInfo{
@@ -309,7 +326,7 @@ func (e *exportInfoMap) rehydrateCachedInfo(ch *checker.Checker, info CachedSymb
 		info.exportKind,
 		info.targetFlags,
 		info.isFromPackageJson,
-	}
+	}, true
 }
 
 func getNamesForExportedSymbol(defaultExport *ast.Symbol, ch *checker.Checker, scriptTarget core.ScriptTarget) []string {