Always generate configFileDiag if file is going to be added to configured project (#37443)

Fixes #30623

Author: sheetalkamat

src/server/editorServices.ts

@@ -3017,6 +3017,13 @@ namespace ts.server {
             // At this point if file is part of any any configured or external project, then it would be present in the containing projects
             // So if it still doesnt have any containing projects, it needs to be part of inferred project
             if (info.isOrphan()) {
+                // Even though this info did not belong to any of the configured projects, send the config file diag
+                if (isArray(retainProjects)) {
+                    retainProjects.forEach(project => this.sendConfigFileDiagEvent(project, info.fileName));
+                }
+                else if (retainProjects) {
+                    this.sendConfigFileDiagEvent(retainProjects, info.fileName);
+                }
                 Debug.assert(this.openFiles.has(info.path));
                 this.assignOrphanScriptInfoToInferredProject(info, this.openFiles.get(info.path));
             }

src/testRunner/unittests/tsserver/projectErrors.ts

@@ -608,6 +608,10 @@ declare module '@custom/plugin' {
                 path: "/a/b/test.ts",
                 content: "let x = 10"
             };
+            const file3: File = {
+                path: "/a/b/test2.ts",
+                content: "let xy = 10"
+            };
             const configFile: File = {
                 path: "/a/b/tsconfig.json",
                 content: `{
@@ -618,9 +622,20 @@ declare module '@custom/plugin' {
                     "files": ["app.ts"]
                 }`
             };
-            const serverEventManager = new TestServerEventManager([file, file2, libFile, configFile]);
+            const serverEventManager = new TestServerEventManager([file, file2, file3, libFile, configFile]);
             openFilesForSession([file2], serverEventManager.session);
+            serverEventManager.checkSingleConfigFileDiagEvent(configFile.path, file2.path, [
+                getUnknownCompilerOptionDiagnostic(configFile, "foo"),
+                getUnknownCompilerOptionDiagnostic(configFile, "allowJS", "allowJs")
+            ]);
+            openFilesForSession([file], serverEventManager.session);
+            // We generate only if project is created when opening file from the project
             serverEventManager.hasZeroEvent("configFileDiag");
+            openFilesForSession([file3], serverEventManager.session);
+            serverEventManager.checkSingleConfigFileDiagEvent(configFile.path, file3.path, [
+                getUnknownCompilerOptionDiagnostic(configFile, "foo"),
+                getUnknownCompilerOptionDiagnostic(configFile, "allowJS", "allowJs")
+            ]);
         });
 
         it("are not generated when the config file has errors but suppressDiagnosticEvents is true", () => {
@@ -651,16 +666,25 @@ declare module '@custom/plugin' {
                 path: "/a/b/test.ts",
                 content: "let x = 10"
             };
+            const file3: File = {
+                path: "/a/b/test2.ts",
+                content: "let xy = 10"
+            };
             const configFile: File = {
                 path: "/a/b/tsconfig.json",
                 content: `{
                     "files": ["app.ts"]
                 }`
             };
 
-            const serverEventManager = new TestServerEventManager([file, file2, libFile, configFile]);
+            const serverEventManager = new TestServerEventManager([file, file2, file3, libFile, configFile]);
             openFilesForSession([file2], serverEventManager.session);
+            serverEventManager.checkSingleConfigFileDiagEvent(configFile.path, file2.path, emptyArray);
+            openFilesForSession([file], serverEventManager.session);
+            // We generate only if project is created when opening file from the project
             serverEventManager.hasZeroEvent("configFileDiag");
+            openFilesForSession([file3], serverEventManager.session);
+            serverEventManager.checkSingleConfigFileDiagEvent(configFile.path, file3.path, emptyArray);
         });
 
         it("contains the project reference errors", () => {