Send message to lsp client when runtime was not found.

Author: nojaf

server/src/bsc-args/rewatch.ts

@@ -1,6 +1,7 @@
 import * as path from "path";
 import * as utils from "../utils";
 import * as cp from "node:child_process";
+import * as p from "vscode-languageserver-protocol";
 import semver from "semver";
 import {
   debug,
@@ -9,6 +10,7 @@ import {
 import type { projectFiles } from "../projectFiles";
 import config from "../config";
 import { findRescriptRuntimesInProject } from "../find-runtime";
+import { jsonrpcVersion } from "../constants";
 
 export type RewatchCompilerArgs = {
   compiler_args: Array<string>;
@@ -54,6 +56,7 @@ async function getRuntimePath(
 }
 
 export async function getRewatchBscArgs(
+  send: (msg: p.Message) => void,
   projectsFiles: Map<string, projectFiles>,
   entry: IncrementallyCompiledFileInfo,
 ): Promise<RewatchCompilerArgs | null> {
@@ -129,17 +132,33 @@ export async function getRewatchBscArgs(
       (env as any)["RESCRIPT_BSC_EXE"] = bscExe;
     }
 
-    let rescriptRuntime: string | null = await getRuntimePath(entry);
-
+    // For ReScript >= 12.0.0-beta.11 we need to set RESCRIPT_RUNTIME
     if (
-      rescriptRuntime !== null &&
       semver.satisfies(project.rescriptVersion, ">=12.0.0-beta.11", {
         includePrerelease: true,
       })
     ) {
-      (env as any)["RESCRIPT_RUNTIME"] = rescriptRuntime;
-    } else {
-      // TODO: if no runtime was found, we should let the user know
+      let rescriptRuntime: string | null = await getRuntimePath(entry);
+
+      if (rescriptRuntime !== null) {
+        (env as any)["RESCRIPT_RUNTIME"] = rescriptRuntime;
+      } else {
+        // If no runtime was found, we should let the user know.
+        let params: p.ShowMessageParams = {
+          type: p.MessageType.Error,
+          message:
+            `[Incremental type checking] The @rescript/runtime package was not found in your project. ` +
+            `It is normally included with ReScript, but either it's missing or could not be detected. ` +
+            `Check that it exists in your dependencies, or configure 'rescript.settings.runtimePath' to point to it. ` +
+            `Without this package, incremental type checking may not work as expected.`,
+        };
+        let message: p.NotificationMessage = {
+          jsonrpc: jsonrpcVersion,
+          method: "window/showMessage",
+          params: params,
+        };
+        send(message);
+      }
     }
 
     const compilerArgs = JSON.parse(

server/src/incrementalCompilation.ts

@@ -180,11 +180,12 @@ export function cleanUpIncrementalFiles(
 }
 
 export async function getBscArgs(
+  send: (msg: p.Message) => void,
   entry: IncrementallyCompiledFileInfo,
 ): Promise<BsbCompilerArgs | RewatchCompilerArgs | null> {
   return entry.buildSystem === "bsb"
     ? await getBsbBscArgs(entry)
-    : await getRewatchBscArgs(projectsFiles, entry);
+    : await getRewatchBscArgs(send, projectsFiles, entry);
 }
 
 function argCouples(argList: string[]): string[][] {
@@ -331,6 +332,7 @@ function triggerIncrementalCompilationOfFile(
     };
 
     incrementalFileCacheEntry.project.callArgs = figureOutBscArgs(
+      send,
       incrementalFileCacheEntry,
     );
     originalTypeFileToFilePath.set(
@@ -371,7 +373,10 @@ function verifyTriggerToken(filePath: string, triggerToken: number): boolean {
 
 const isWindows = os.platform() === "win32";
 
-async function figureOutBscArgs(entry: IncrementallyCompiledFileInfo) {
+async function figureOutBscArgs(
+  send: (msg: p.Message) => void,
+  entry: IncrementallyCompiledFileInfo,
+) {
   const project = projectsFiles.get(entry.project.rootPath);
   if (project?.rescriptVersion == null) {
     if (debug()) {
@@ -382,7 +387,7 @@ async function figureOutBscArgs(entry: IncrementallyCompiledFileInfo) {
     }
     return null;
   }
-  const res = await getBscArgs(entry);
+  const res = await getBscArgs(send, entry);
   if (res == null) return null;
   let astArgs: Array<Array<string>> = [];
   let buildArgs: Array<Array<string>> = [];
@@ -483,7 +488,7 @@ async function compileContents(
   const triggerToken = entry.compilation?.triggerToken;
   let callArgs = await entry.project.callArgs;
   if (callArgs == null) {
-    const callArgsRetried = await figureOutBscArgs(entry);
+    const callArgsRetried = await figureOutBscArgs(send, entry);
     if (callArgsRetried != null) {
       callArgs = callArgsRetried;
       entry.project.callArgs = Promise.resolve(callArgsRetried);