Updates to ts-plugin README, and a .dir-locals.el

.dir-locals.el

@@ -0,0 +1,6 @@
+((typescript-mode
+  . ((eval . (setq tide-tsserver-executable
+                   (concat
+                    (let ((d (dir-locals-find-file ".")))
+                      (if (stringp d) d (car d)))
+                    "node_modules/typescript/lib/tsserver.js"))))))

packages/ts-plugin/README.md

@@ -40,12 +40,55 @@ then `yarn install`.
 
 ### Emacs with Tide
 
-It should Just Work.
+It should Just Work, if the `node_modules` next to `tsconfig.json` has
+a `typescript/` subdirectory.
+
+If no such `typescript/` subdirectory exists in `node_modules`, then
+because
+[tsserver loads plugins from relative to tsserver.js rather than tsconfig.json](https://github.com/microsoft/TypeScript/issues/42688),
+you will have to tell `tide-mode` about where your project's
+`tsserver` lives.
+
+One easy way to do that is to create a symlink in your `node_modules`:
+
+```shell
+ln -s /FULL/PATH/TO/YOUR/PROJECT/node_modules/typescript ./node_modules/
+```
+
+Another way to do it is to put a `.dir-locals.el` file in your project
+root, containing
+
+```elisp
+((tide-mode
+  . ((tide-tsserver-executable
+      . "/FULL/PATH/TO/YOUR/PROJECT/node_modules/typescript/bin/tsserver"))))
+```
+
+I don't know of any way of automatically resolving a relative path
+specification with respect to the directory containing
+`.dir-locals.el` without using `eval`, but if you're happy to do so,
+you can use the following:
+
+```elisp
+((typescript-mode
+  . ((eval . (setq tide-tsserver-executable
+                   (concat
+                    (let ((d (dir-locals-find-file ".")))
+                      (if (stringp d) d (car d)))
+                    "node_modules/typescript/lib/tsserver.js"))))))
+```
+
+If you use the `.dir-locals.el` methods, you may need to run
+`tide-restart-server` once after opening the first TypeScript file in
+your project (and then close and re-open that TypeScript file).
 
 ### Visual Studio Code
 
-After `yarn install`, you will have a `node_modules/typescript`
-directory.
+After `yarn install`, if you have a `node_modules/typescript`
+directory, then the following will work. (Otherwise, there may not be
+an option to select "Use Workspace Version", and you may need to
+symlink a `typescript` directory into `node_modules` as described for
+Emacs Tide above.)
 
 Open VS Code, and select the version of TypeScript contained therein
 by following instructions
@@ -60,3 +103,25 @@ file containing:
     {
         "typescript.tsdk": "node_modules/typescript/lib"
     }
+
+## Debugging
+
+You can get verbose logs from Tide's tsserver by setting the Emacs
+variable `tide-tsserver-process-environment`:
+
+```elisp
+(setq tide-tsserver-process-environment '("TSS_LOG=-file /tmp/tss.log"))
+```
+
+You can also enable "verbose" output, if that's useful:
+
+```elisp
+(setq tide-tsserver-process-environment '("TSS_LOG=-level verbose -file /tmp/tss.log"))
+```
+
+Finally, you can set these options in a `.dir-locals.el` file, too:
+
+```elisp
+((typescript-mode
+  . ((tide-tsserver-process-environment . ("TSS_LOG=-level verbose -file /tmp/tss.log")))))
+```