node.getText(sourceFile) crashes when node.kind == Identifier

[mmorearty]

TypeScript Version: 2.7.0-dev.20171101

This program uses the TypeScript compiler's API to walk the AST (abstract syntax tree) of some parsed TypeScript source code. Compilation works fine; when you run the program, it should display the node type (SyntaxKind) and text of every node in the AST.

Code

import * as fs from "fs";
import * as ts from "typescript";

const source = 'console.log("hello, world")';

const host: ts.LanguageServiceHost = {
    getCompilationSettings: () => ({}),
    getScriptFileNames: () => ["example.ts"],
    getScriptVersion: (filename: string) => "helloworld",
    getScriptSnapshot: (filename: string): ts.IScriptSnapshot => {
        return {
            getText: (start: number, end: number) => source.slice(start, end),
            getLength: () => source.length,
            getChangeRange: (oldSnapshot: ts.IScriptSnapshot) => undefined
        };
    },
    getCurrentDirectory: process.cwd,
    getDefaultLibFileName: (options: ts.CompilerOptions) => "node_modules/typescript/lib/lib.d.ts",
    getNewLine: () => "\n"
};

const languageService = ts.createLanguageService(host);
const sourceFile = ts.createSourceFile("example.ts", source, ts.ScriptTarget.ES2015);

function visit(parent: ts.Node, node: ts.Node, ind: string) {
    // This next line will crash when it reaches an Identifier node for the identifier 'console':
    console.log(ind + ts.SyntaxKind[node.kind] + ":" + node.getText(sourceFile).replace(/\n/g, "\\n"));

    // If you use this version instead, it will not crash, because sourceFile() is passed in to node.getStart():
    //console.log(ind + ts.SyntaxKind[node.kind] + ":" + source.substring(node.getStart(sourceFile), node.getEnd()).replace(/\n/g, "\\n"));

    ts.forEachChild(node, (child: ts.Node) => {
        visit(node, child, ind + "  ");
    });
}

visit(null, sourceFile, "");

Expected behavior:
This program uses the TypeScript compiler's API. Compilation works fine; when you run the program, it should display the node type (SyntaxKind) and text of every node in the AST.

Actual behavior:
It displays the first several nodes of the AST correctly. But when it reaches the node for the console identifier, it crashes:

SourceFile:console.log("hello, world")
  ExpressionStatement:console.log("hello, world")
    CallExpression:console.log("hello, world")
      PropertyAccessExpression:console.log
/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:7479
        return ts.skipTrivia((sourceFile || getSourceFileOfNode(node)).text, node.pos);
                                                                       ^

TypeError: Cannot read property 'text' of undefined
    at Object.getTokenPosOfNode (/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:7479:72)
    at IdentifierObject.TokenOrIdentifierObject.getStart (/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:95162:23)
    at IdentifierObject.TokenOrIdentifierObject.getText (/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:95183:77)
    at visit (/Users/mikemorearty/src/typescript/crashdemo/index.js:24:61)
    at /Users/mikemorearty/src/typescript/crashdemo/index.js:28:9
    at visitNode (/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:12655:24)
    at Object.forEachChild (/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:12786:24)
    at visit (/Users/mikemorearty/src/typescript/crashdemo/index.js:27:8)
    at /Users/mikemorearty/src/typescript/crashdemo/index.js:28:9
    at visitNode (/Users/mikemorearty/src/typescript/crashdemo/node_modules/typescript/lib/typescript.js:12655:24)

The fix is easy: In src/services/services.ts line 279, sourceFile needs to be passed in to this.getStart(). In other words:

diff --git a/src/services/services.ts b/src/services/services.ts
index 06edd621e9..cd6fe86771 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -276,7 +276,10 @@ namespace ts {
         }

         public getText(sourceFile?: SourceFile): string {
-            return (sourceFile || this.getSourceFile()).text.substring(this.getStart(), this.getEnd());
+            if (!sourceFile) {
+                sourceFile = this.getSourceFile();
+            }
+            return sourceFile.text.substring(this.getStart(sourceFile), this.getEnd());
         }

         public getChildCount(): number {

In fact, this same change already exists farther up in the same file, in class NodeObject.

[mhegazy]

A PR would be appreciated.