internal/lsp/protocol/typescript: update documentation and generated code

Modifies README.md to be clearer about the necessary version of the
typescript compiler. Adds generated code that allows unmarshalling
type errors on Initialize messages.

See https://go-review.googlesource.com/c/tools/+/310109
Fixes  golang/go#35316

Change-Id: Id128c23e807e67e02d1354edaa0b164c9d36101c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/310753
Trust: Peter Weinberger <[email protected]>
Trust: Rebecca Stambler <[email protected]>
Reviewed-by: Rebecca Stambler <[email protected]>

Author: pjweinbgo

internal/lsp/protocol/tsclient.go

@@ -3,14 +3,15 @@
 ## Setup
 
 Make sure `node` and `tsc` are installed and in your PATH. There are detailed instructions below.
+(`tsc -v` should be at least `4.2.4`.)
 Get the typescript code for the jsonrpc protocol with
 
 `git clone [email protected]:microsoft vscode-languageserver-node.git` or
 `git clone https://github.com/microsoft/vscode-languageserver-node.git`
 
-`util.ts`` expects it to be in your HOME directory
+`util.ts` expects it to be in your HOME directory
 
-If you want to reproduce the existing files you need to be on a branch with the same git hash, for instance, `git checkout 7b90c29`
+If you want to reproduce the existing files you need to be on a branch with the same git hash that `util.ts` expects, for instance, `git checkout 7b90c29`
 
 ## Usage
 
@@ -50,5 +51,5 @@ the generated files and stored in the variable `gitHash` in `go.ts`. It is check
     1. This will likely give warning messages that indicate you've failed to set up a project. Ignore them.
     2. Your home directory will now have new directories `.npm` and `node_modules` (and a `package_lock.json` file)
     3. The typescript executable `tsc` will be in `node_modules/.bin`, so put that directory in your path.
-    4. `tsc -v` should print "Version 3.7.2" (or later). If not you may (as I did) have an obsolete tsc earlier in your path.
+    4. `tsc -v` should print "Version 4.2.4" (or later). If not you may (as I did) have an obsolete tsc earlier in your path.
 6. `npm install @types/node` (Without this there will be many incomprehensible typescript error messages.)

internal/lsp/protocol/tsprotocol.go

@@ -916,18 +916,20 @@ function goUnionType(n: ts.UnionTypeNode, nm: string): string {
       if (nm == 'textDocument/documentSymbol') {
         return `[]interface{} ${help}`;
       }
-      if (aa == 'TypeReference' && bb == 'ArrayType' && cc == 'NullKeyword') {
+      if (aa == 'TypeReference' && bb == 'ArrayType' && (cc == 'NullKeyword' || cc === 'LiteralType')) {
         return `${goType(n.types[0], 'd')} ${help}`;
       }
       if (aa == 'TypeReference' && bb == aa && cc == 'ArrayType') {
         // should check that this is Hover.Contents
         return `${goType(n.types[0], 'e')} ${help}`;
       }
-      if (aa == 'ArrayType' && bb == 'TypeReference' && cc == 'NullKeyword') {
+      if (aa == 'ArrayType' && bb == 'TypeReference' && (cc == 'NullKeyword' || cc === 'LiteralType')) {
         // check this is nm == 'textDocument/completion'
         return `${goType(n.types[1], 'f')} ${help}`;
       }
       if (aa == 'LiteralType' && bb == aa && cc == aa) return `string ${help}`;
+      // keep this for diagnosing unexpected interface{} results
+      // console.log(`931, interface{} for ${aa}/${goType(n.types[0], 'g')},${bb}/${goType(n.types[1], 'h')},${cc}/${goType(n.types[2], 'i')} ${nm}`);
       break;
     }
     case 4:
@@ -1206,6 +1208,14 @@ function goReq(side: side, m: string) {
     if err := json.Unmarshal(r.Params(), &params); err != nil {
       return true, sendParseError(ctx, reply, err)
     }`;
+    if (a === 'ParamInitialize') {
+      case1 = `var params ${a}
+    if err := json.Unmarshal(r.Params(), &params); err != nil {
+      if _, ok := err.(*json.UnmarshalTypeError); !ok {
+        return true, sendParseError(ctx, reply, err)
+      }
+    }`;
+    }
   }
   const arg2 = a == '' ? '' : ', &params';
   // if case2 is not explicitly typed string, typescript makes it a union of strings