diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 90b516dadfc..dd05b562cff 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -2195,6 +2195,70 @@ namespace ts.server {
             return this.filenameToScriptInfo.get(fileName);
         }
 
+        /*@internal*/
+        getDocumentPositionMapper(fileName: string, project: Project): DocumentPositionMapper | undefined {
+            const declarationInfo = this.getOrCreateScriptInfoNotOpenedByClient(fileName, project.currentDirectory, project.directoryStructureHost);
+            if (!declarationInfo) return undefined;
+
+            declarationInfo.getSnapshot(); // Ensure synchronized
+            const existingMapper = declarationInfo.textStorage.mapper;
+            if (existingMapper !== undefined) {
+                return existingMapper ? existingMapper : undefined;
+            }
+
+            // Create the mapper
+            declarationInfo.mapInfo = undefined;
+
+            let readMapFile: ((fileName: string) => string | undefined) | undefined = fileName => {
+                const mapInfo = this.getOrCreateScriptInfoNotOpenedByClient(fileName, project.currentDirectory, project.directoryStructureHost);
+                if (!mapInfo) return undefined;
+                declarationInfo.mapInfo = mapInfo;
+                const snap = mapInfo.getSnapshot();
+                return snap.getText(0, snap.getLength());
+            };
+            const projectName = project.projectName;
+            const mapper = getDocumentPositionMapper(
+                { getCanonicalFileName: this.toCanonicalFileName, log: s => this.logger.info(s), getSourceFileLike: f => this.getSourceFileLike(f, projectName) },
+                declarationInfo.fileName,
+                declarationInfo.textStorage.getLineInfo(),
+                readMapFile
+            );
+            readMapFile = undefined; // Remove ref to project
+            declarationInfo.textStorage.mapper = mapper || false;
+            return mapper;
+        }
+
+        /*@internal*/
+        getSourceFileLike(fileName: string, projectName: string | Project) {
+            const project = (projectName as Project).projectName ? projectName as Project : this.findProject(projectName as string);
+            if (project) {
+                const path = project.toPath(fileName);
+                const sourceFile = project.getSourceFile(path);
+                if (sourceFile && sourceFile.resolvedPath === path) return sourceFile;
+            }
+
+            // Need to look for other files.
+            const info = this.getOrCreateScriptInfoNotOpenedByClient(fileName, (project || this).currentDirectory, project ? project.directoryStructureHost : this.host);
+            if (!info) return undefined;
+
+            // Key doesnt matter since its only for text and lines
+            if (info.cacheSourceFile) return info.cacheSourceFile.sourceFile;
+            if (info.textStorage.sourceFileLike) return info.textStorage.sourceFileLike;
+
+            info.textStorage.sourceFileLike = {
+                get text() {
+                    Debug.fail("shouldnt need text");
+                    return "";
+                },
+                getLineAndCharacterOfPosition: pos => {
+                    const lineOffset = info.positionToLineOffset(pos);
+                    return { line: lineOffset.line - 1, character: lineOffset.offset - 1 };
+                },
+                getPositionOfLineAndCharacter: (line, character) => info.lineOffsetToPosition(line + 1, character + 1)
+            };
+            return info.textStorage.sourceFileLike;
+        }
+
         setHostConfiguration(args: protocol.ConfigureRequestArguments) {
             if (args.file) {
                 const info = this.getScriptInfoForNormalizedPath(toNormalizedPath(args.file));
diff --git a/src/server/project.ts b/src/server/project.ts
index 566a2b9abe9..6ea9589cb4b 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -505,62 +505,12 @@ namespace ts.server {
 
         /*@internal*/
         getDocumentPositionMapper(fileName: string): DocumentPositionMapper | undefined {
-            const declarationInfo = this.projectService.getOrCreateScriptInfoNotOpenedByClient(fileName, this.currentDirectory, this.directoryStructureHost);
-            if (!declarationInfo) return undefined;
-
-            declarationInfo.getSnapshot(); // Ensure synchronized
-            const existingMapper = declarationInfo.textStorage.mapper;
-            if (existingMapper !== undefined) {
-                return existingMapper ? existingMapper : undefined;
-            }
-
-            // Create the mapper
-            declarationInfo.mapInfo = undefined;
-
-            const mapper = getDocumentPositionMapper({
-                getCanonicalFileName: this.projectService.toCanonicalFileName,
-                log: s => this.log(s),
-                readMapFile: f => this.readMapFile(f, declarationInfo),
-                getSourceFileLike: f => this.getSourceFileLike(f)
-            }, declarationInfo.fileName, declarationInfo.textStorage.getLineInfo());
-            declarationInfo.textStorage.mapper = mapper || false;
-            return mapper;
-        }
-
-        private readMapFile(fileName: string, declarationInfo: ScriptInfo) {
-            const mapInfo = this.projectService.getOrCreateScriptInfoNotOpenedByClient(fileName, this.currentDirectory, this.directoryStructureHost);
-            if (!mapInfo) return undefined;
-            declarationInfo.mapInfo = mapInfo;
-            const snap = mapInfo.getSnapshot();
-            return snap.getText(0, snap.getLength());
+            return this.projectService.getDocumentPositionMapper(fileName, this);
         }
 
         /*@internal*/
         getSourceFileLike(fileName: string) {
-            const path = this.toPath(fileName);
-            const sourceFile = this.getSourceFile(path);
-            if (sourceFile && sourceFile.resolvedPath === path) return sourceFile;
-
-            // Need to look for other files.
-            const info = this.projectService.getOrCreateScriptInfoNotOpenedByClient(fileName, this.currentDirectory, this.directoryStructureHost);
-            if (!info) return undefined;
-
-            // Key doesnt matter since its only for text and lines
-            if (info.cacheSourceFile) return info.cacheSourceFile.sourceFile;
-            if (info.textStorage.sourceFileLike) return info.textStorage.sourceFileLike;
-
-            info.textStorage.sourceFileLike = {
-                get text() {
-                    Debug.fail("shouldnt need text");
-                    return "";
-                },
-                getLineAndCharacterOfPosition: pos => {
-                    const lineOffset = info.positionToLineOffset(pos);
-                    return { line: lineOffset.line - 1, character: lineOffset.offset - 1 };
-                },
-                getPositionOfLineAndCharacter: (line, character) => info.lineOffsetToPosition(line + 1, character + 1)
-            };
-            return info.textStorage.sourceFileLike;
+            return this.projectService.getSourceFileLike(fileName, this);
         }
 
         private shouldEmitFile(scriptInfo: ScriptInfo) {
diff --git a/src/services/sourcemaps.ts b/src/services/sourcemaps.ts
index c679688e6c0..00d2696abf5 100644
--- a/src/services/sourcemaps.ts
+++ b/src/services/sourcemaps.ts
@@ -42,12 +42,12 @@ namespace ts {
             }
             else if (host.readFile) {
                 const file = getSourceFileLike(fileName);
-                mapper = file && ts.getDocumentPositionMapper({
-                    getSourceFileLike,
-                    getCanonicalFileName,
-                    log: s => host.log(s),
-                    readMapFile: f => !host.fileExists || host.fileExists(f) ? host.readFile!(f) : undefined
-                }, fileName, getLineInfo(file.text, getLineStarts(file)));
+                mapper = file && ts.getDocumentPositionMapper(
+                    { getSourceFileLike, getCanonicalFileName, log: s => host.log(s) },
+                    fileName,
+                    getLineInfo(file.text, getLineStarts(file)),
+                    f => !host.fileExists || host.fileExists(f) ? host.readFile!(f) : undefined
+                );
             }
             documentPositionMappers.set(path, mapper || identitySourceMapConsumer);
             return mapper || identitySourceMapConsumer;
@@ -118,7 +118,6 @@ namespace ts {
         }
 
         function toLineColumnOffset(fileName: string, position: number): LineAndCharacter {
-            // TODO:: shkamat
             const file = getSourceFileLike(fileName)!; // TODO: GH#18217
             return file.getLineAndCharacterOfPosition(position);
         }
@@ -129,11 +128,11 @@ namespace ts {
         }
     }
 
-    export interface GetDocumentPositionMapperHost extends DocumentPositionMapperHost {
-        readMapFile(fileName: string): string | undefined;
-    }
-
-    export function getDocumentPositionMapper(host: GetDocumentPositionMapperHost, generatedFileName: string, generatedFileLineInfo: LineInfo) {
+    export function getDocumentPositionMapper(
+        host: DocumentPositionMapperHost,
+        generatedFileName: string,
+        generatedFileLineInfo: LineInfo,
+        readMapFile: (fileName: string) => string | undefined) {
         let mapFileName = tryGetSourceMappingURL(generatedFileLineInfo);
         if (mapFileName) {
             const match = base64UrlRegExp.exec(mapFileName);
@@ -153,7 +152,7 @@ namespace ts {
         possibleMapLocations.push(generatedFileName + ".map");
         for (const location of possibleMapLocations) {
             const mapFileName = getNormalizedAbsolutePath(location, getDirectoryPath(generatedFileName));
-            const mapFileContents = host.readMapFile(mapFileName);
+            const mapFileContents = readMapFile(mapFileName);
             if (mapFileContents) {
                 return convertDocumentToSourceMapper(host, mapFileContents, mapFileName);
             }
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index b788d46ac9f..1a104716c28 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -8210,7 +8210,6 @@ declare namespace ts.server {
         getGlobalProjectErrors(): ReadonlyArray<Diagnostic>;
         getAllProjectErrors(): ReadonlyArray<Diagnostic>;
         getLanguageService(ensureSynchronized?: boolean): LanguageService;
-        private readMapFile;
         private shouldEmitFile;
         getCompileOnSaveAffectedFileList(scriptInfo: ScriptInfo): string[];
         /**