diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index b649527572e..2f3c6204937 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -867,7 +867,7 @@ namespace ts.server {
         private doEnsureDefaultProjectForFile(fileName: NormalizedPath): Project {
             this.ensureProjectStructuresUptoDate();
             const scriptInfo = this.getScriptInfoForNormalizedPath(fileName);
-            return scriptInfo ? scriptInfo.getDefaultProject() : Errors.ThrowNoProject();
+            return scriptInfo ? scriptInfo.getDefaultProject() : (this.logErrorForScriptInfoNotFound(fileName), Errors.ThrowNoProject());
         }
 
         getScriptInfoEnsuringProjectsUptoDate(uncheckedFileName: string) {
@@ -1966,6 +1966,12 @@ namespace ts.server {
             return configProject && configProject.getCompilerOptions().configFile;
         }
 
+        /* @internal */
+        logErrorForScriptInfoNotFound(fileName: string): void {
+            const names = arrayFrom(this.filenameToScriptInfo.entries()).map(([path, scriptInfo]) => ({ path, fileName: scriptInfo.fileName }));
+            this.logger.msg(`Could not find file ${JSON.stringify(fileName)}.\nAll files are: ${JSON.stringify(names)}`, Msg.Err);
+        }
+
         /**
          * Returns the projects that contain script info through SymLink
          * Note that this does not return projects in info.containingProjects
diff --git a/src/server/session.ts b/src/server/session.ts
index da4808c31f6..42d3994db09 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -1157,7 +1157,9 @@ namespace ts.server {
                     this.projectService.getScriptInfoEnsuringProjectsUptoDate(args.file) :
                     this.projectService.getScriptInfo(args.file);
                 if (!scriptInfo) {
-                    return ignoreNoProjectError ? emptyArray : Errors.ThrowNoProject();
+                    if (ignoreNoProjectError) return emptyArray;
+                    this.projectService.logErrorForScriptInfoNotFound(args.file);
+                    return Errors.ThrowNoProject();
                 }
                 projects = scriptInfo.containingProjects;
                 symLinkedProjects = this.projectService.getSymlinkedProjects(scriptInfo);
@@ -1165,6 +1167,7 @@ namespace ts.server {
             // filter handles case when 'projects' is undefined
             projects = filter(projects, p => p.languageServiceEnabled && !p.isOrphan());
             if (!ignoreNoProjectError && (!projects || !projects.length) && !symLinkedProjects) {
+                this.projectService.logErrorForScriptInfoNotFound(args.file);
                 return Errors.ThrowNoProject();
             }
             return symLinkedProjects ? { projects: projects!, symLinkedProjects } : projects!; // TODO: GH#18217
@@ -1908,8 +1911,17 @@ namespace ts.server {
             return textChanges.map(change => this.mapTextChangeToCodeEdit(change));
         }
 
-        private mapTextChangeToCodeEdit(change: FileTextChanges): protocol.FileCodeEdits {
-            return mapTextChangesToCodeEdits(change, this.projectService.getScriptInfoOrConfig(change.fileName));
+        private mapTextChangeToCodeEdit(textChanges: FileTextChanges): protocol.FileCodeEdits {
+            const scriptInfo = this.projectService.getScriptInfoOrConfig(textChanges.fileName);
+            if (!!textChanges.isNewFile === !!scriptInfo) {
+                if (!scriptInfo) { // and !isNewFile
+                    this.projectService.logErrorForScriptInfoNotFound(textChanges.fileName);
+                }
+                Debug.fail("Expected isNewFile for (only) new files. " + JSON.stringify({ isNewFile: !!textChanges.isNewFile, hasScriptInfo: !!scriptInfo }));
+            }
+            return scriptInfo
+                ? { fileName: textChanges.fileName, textChanges: textChanges.textChanges.map(textChange => convertTextChangeToCodeEdit(textChange, scriptInfo)) }
+                : convertNewFileTextChangeToCodeEdit(textChanges);
         }
 
         private convertTextChangeToCodeEdit(change: TextChange, scriptInfo: ScriptInfo): protocol.CodeEdit {
@@ -2431,13 +2443,6 @@ namespace ts.server {
         return { file: fileName, start: scriptInfo.positionToLineOffset(textSpan.start), end: scriptInfo.positionToLineOffset(textSpanEnd(textSpan)) };
     }
 
-    function mapTextChangesToCodeEdits(textChanges: FileTextChanges, scriptInfo: ScriptInfoOrConfig | undefined): protocol.FileCodeEdits {
-        Debug.assert(!!textChanges.isNewFile === !scriptInfo, "Expected isNewFile for (only) new files", () => JSON.stringify({ isNewFile: !!textChanges.isNewFile, hasScriptInfo: !!scriptInfo }));
-        return scriptInfo
-            ? { fileName: textChanges.fileName, textChanges: textChanges.textChanges.map(textChange => convertTextChangeToCodeEdit(textChange, scriptInfo)) }
-            : convertNewFileTextChangeToCodeEdit(textChanges);
-    }
-
     function convertTextChangeToCodeEdit(change: TextChange, scriptInfo: ScriptInfoOrConfig): protocol.CodeEdit {
         return { start: positionToLineOffset(scriptInfo, change.span.start), end: positionToLineOffset(scriptInfo, textSpanEnd(change.span)), newText: change.newText };
     }