diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index d98aa948113..5c70c7be8bf 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -2197,8 +2197,8 @@ namespace ts.server {
         }
 
         /*@internal*/
-        getDocumentPositionMapper(fileName: string, project: Project): DocumentPositionMapper | undefined {
-            const declarationInfo = this.getOrCreateScriptInfoNotOpenedByClient(fileName, project.currentDirectory, project.directoryStructureHost);
+        getDocumentPositionMapper(project: Project, generatedFileName: string, sourceFileName?: string): DocumentPositionMapper | undefined {
+            const declarationInfo = this.getOrCreateScriptInfoNotOpenedByClient(generatedFileName, project.currentDirectory, project.directoryStructureHost);
             if (!declarationInfo) return undefined;
 
             declarationInfo.getSnapshot(); // Ensure synchronized
@@ -2210,7 +2210,6 @@ namespace ts.server {
             // Create the mapper
             declarationInfo.mapInfo = undefined;
 
-            // TODO: shkamat Lifetime of declarationInfo and mapInfo
             let readMapFile: ((fileName: string) => string | undefined) | undefined = fileName => {
                 const mapInfo = this.getOrCreateScriptInfoNotOpenedByClient(fileName, project.currentDirectory, project.directoryStructureHost);
                 if (!mapInfo) return undefined;
@@ -2227,6 +2226,11 @@ namespace ts.server {
             );
             readMapFile = undefined; // Remove ref to project
             declarationInfo.mapper = mapper || false;
+            if (sourceFileName && mapper) {
+                // Attach as source
+                const sourceInfo = this.getOrCreateScriptInfoNotOpenedByClient(sourceFileName, project.currentDirectory, project.directoryStructureHost)!;
+                (declarationInfo.mapInfo!.sourceInfos || (declarationInfo.mapInfo!.sourceInfos = createMap())).set(sourceInfo.path, true);
+            }
             return mapper;
         }
 
@@ -2609,13 +2613,25 @@ namespace ts.server {
         private removeOrphanScriptInfos() {
             const toRemoveScriptInfos = cloneMap(this.filenameToScriptInfo);
             this.filenameToScriptInfo.forEach(info => {
-                if (info.isScriptOpen() || !info.isOrphan()) {
-                    toRemoveScriptInfos.delete(info.path);
-                    if (info.mapInfo) {
-                        toRemoveScriptInfos.delete(info.mapInfo.path);
-                        if (info.mapInfo.sourceInfos) {
-                            info.mapInfo.sourceInfos.forEach((_value, path) => toRemoveScriptInfos.delete(path));
-                        }
+                // If script info is open or orphan, retain it and its dependencies
+                if (!info.isScriptOpen() && info.isOrphan()) {
+                    // Otherwise if there is any source info that is alive, this alive too
+                    if (!info.mapInfo || !info.mapInfo.sourceInfos) return;
+                    if (!forEachKey(info.mapInfo.sourceInfos, path => {
+                        const info = this.getScriptInfoForPath(path as Path)!;
+                        return info.isScriptOpen() || !info.isOrphan();
+                    })) {
+                        return;
+                    }
+                }
+
+                // Retain this script info
+                toRemoveScriptInfos.delete(info.path);
+                if (info.mapInfo) {
+                    // And map file info and source infos
+                    toRemoveScriptInfos.delete(info.mapInfo.path);
+                    if (info.mapInfo.sourceInfos) {
+                        info.mapInfo.sourceInfos.forEach((_value, path) => toRemoveScriptInfos.delete(path));
                     }
                 }
             });
diff --git a/src/server/project.ts b/src/server/project.ts
index 6ea9589cb4b..a28e9c35be5 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -504,8 +504,8 @@ namespace ts.server {
         }
 
         /*@internal*/
-        getDocumentPositionMapper(fileName: string): DocumentPositionMapper | undefined {
-            return this.projectService.getDocumentPositionMapper(fileName, this);
+        getDocumentPositionMapper(generatedFileName: string, sourceFileName?: string): DocumentPositionMapper | undefined {
+            return this.projectService.getDocumentPositionMapper(this, generatedFileName, sourceFileName);
         }
 
         /*@internal*/
diff --git a/src/server/scriptInfo.ts b/src/server/scriptInfo.ts
index 3d8c737064f..d2f230178d3 100644
--- a/src/server/scriptInfo.ts
+++ b/src/server/scriptInfo.ts
@@ -64,14 +64,20 @@ namespace ts.server {
             this.switchToScriptVersionCache();
         }
 
+        private resetSourceMapInfo() {
+            this.info.mapper = undefined;
+            this.info.sourceFileLike = undefined;
+            this.info.mapInfo = undefined;
+            this.info.sourceInfos = undefined;
+        }
+
         /** Public for testing */
         public useText(newText?: string) {
             this.svc = undefined;
             this.text = newText;
             this.lineMap = undefined;
             this.fileSize = undefined;
-            this.info.mapper = undefined;
-            this.info.sourceFileLike = undefined;
+            this.resetSourceMapInfo();
             this.version.text++;
         }
 
@@ -81,8 +87,7 @@ namespace ts.server {
             this.text = undefined;
             this.lineMap = undefined;
             this.fileSize = undefined;
-            this.info.mapper = undefined;
-            this.info.sourceFileLike = undefined;
+            this.resetSourceMapInfo();
         }
 
         /**
@@ -304,7 +309,7 @@ namespace ts.server {
         /*@internal*/
         sourceInfos?: Map<true>;
         /*@internal*/
-        mapper: DocumentPositionMapper | false | undefined = false;
+        mapper?: DocumentPositionMapper | false;
         /*@internal*/
         sourceFileLike: SourceFileLike | undefined;
 
diff --git a/src/services/services.ts b/src/services/services.ts
index a0c41ffe94d..e8dfb8640e0 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1145,7 +1145,7 @@ namespace ts {
             getProgram,
             fileExists: host.fileExists && (f => host.fileExists!(f)),
             readFile: host.readFile && ((f, encoding) => host.readFile!(f, encoding)),
-            getDocumentPositionMapper: host.getDocumentPositionMapper && (f => host.getDocumentPositionMapper!(f)),
+            getDocumentPositionMapper: host.getDocumentPositionMapper && ((generatedFileName, sourceFileName) => host.getDocumentPositionMapper!(generatedFileName, sourceFileName)),
             getSourceFileLike: host.getSourceFileLike && (f => host.getSourceFileLike!(f)),
             log
         });
diff --git a/src/services/sourcemaps.ts b/src/services/sourcemaps.ts
index 00d2696abf5..ce692fc2184 100644
--- a/src/services/sourcemaps.ts
+++ b/src/services/sourcemaps.ts
@@ -16,7 +16,7 @@ namespace ts {
         fileExists?(path: string): boolean;
         readFile?(path: string, encoding?: string): string | undefined;
         getSourceFileLike?(fileName: string): SourceFileLike | undefined;
-        getDocumentPositionMapper?(fileName: string): DocumentPositionMapper | undefined;
+        getDocumentPositionMapper?(generatedFileName: string, sourceFileName?: string): DocumentPositionMapper | undefined;
         log(s: string): void;
     }
 
@@ -31,20 +31,20 @@ namespace ts {
             return ts.toPath(fileName, currentDirectory, getCanonicalFileName);
         }
 
-        function getDocumentPositionMapper(fileName: string) {
-            const path = toPath(fileName);
+        function getDocumentPositionMapper(generatedFileName: string, sourceFileName?: string) {
+            const path = toPath(generatedFileName);
             const value = documentPositionMappers.get(path);
             if (value) return value;
 
             let mapper: DocumentPositionMapper | undefined;
             if (host.getDocumentPositionMapper) {
-                mapper = host.getDocumentPositionMapper(fileName);
+                mapper = host.getDocumentPositionMapper(generatedFileName, sourceFileName);
             }
             else if (host.readFile) {
-                const file = getSourceFileLike(fileName);
+                const file = getSourceFileLike(generatedFileName);
                 mapper = file && ts.getDocumentPositionMapper(
                     { getSourceFileLike, getCanonicalFileName, log: s => host.log(s) },
-                    fileName,
+                    generatedFileName,
                     getLineInfo(file.text, getLineStarts(file)),
                     f => !host.fileExists || host.fileExists(f) ? host.readFile!(f) : undefined
                 );
@@ -78,7 +78,7 @@ namespace ts {
                 getDeclarationEmitOutputFilePathWorker(info.fileName, program.getCompilerOptions(), currentDirectory, program.getCommonSourceDirectory(), getCanonicalFileName);
             if (declarationPath === undefined) return undefined;
 
-            const newLoc = getDocumentPositionMapper(declarationPath).getGeneratedPosition(info);
+            const newLoc = getDocumentPositionMapper(declarationPath, info.fileName).getGeneratedPosition(info);
             return newLoc === info ? undefined : newLoc;
         }
 
diff --git a/src/services/types.ts b/src/services/types.ts
index d3a8f8cdd52..5100a999306 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -234,7 +234,7 @@ namespace ts {
         writeFile?(fileName: string, content: string): void;
 
         /* @internal */
-        getDocumentPositionMapper?(fileName: string): DocumentPositionMapper | undefined;
+        getDocumentPositionMapper?(generatedFileName: string, sourceFileName?: string): DocumentPositionMapper | undefined;
         /* @internal */
         getSourceFileLike?(fileName: string): SourceFileLike | undefined;
     }
diff --git a/src/testRunner/unittests/tsserverProjectSystem.ts b/src/testRunner/unittests/tsserverProjectSystem.ts
index 217149efd88..59a6f6019d1 100644
--- a/src/testRunner/unittests/tsserverProjectSystem.ts
+++ b/src/testRunner/unittests/tsserverProjectSystem.ts
@@ -10757,7 +10757,6 @@ fn5();`
                 openFilesForSession([dependencyTs, randomFile], session);
                 checkNumberOfProjects(service, { configuredProjects: 2 });
                 checkProjectActualFiles(service.configuredProjects.get(dependencyConfig.path)!, [dependencyTs.path, libFile.path, dependencyConfig.path]);
-                debugger;
                 for (let i = 0; i < 5; i++) {
                     const startSpan = { line: i + 1, offset: 17 };
                     const response = session.executeCommandSeq<protocol.RenameRequest>({