Make early-exit consider throwing as an early exit

rules/earlyExitRule.ts

@@ -1,4 +1,4 @@
-import { isBlock, isCaseOrDefaultClause, isIfStatement, isFunctionScopeBoundary } from 'tsutils';
+import { isBlock, isThrowStatement, isCaseOrDefaultClause, isIfStatement, isFunctionScopeBoundary } from 'tsutils';
 import * as Lint from 'tslint';
 import * as ts from 'typescript';
 
@@ -52,7 +52,7 @@ function walk(ctx: Lint.WalkContext<IOptions>) {
         const thenSize = size(thenStatement, sourceFile);
 
         if (elseStatement === undefined) {
-            if (isLarge(thenSize))
+            if (isLarge(thenSize) && !isThrow(thenStatement))
                 fail(failureString(exit));
             return;
         }
@@ -92,6 +92,14 @@ function size(node: ts.Node, sourceFile: ts.SourceFile): number {
         : diff(node.getStart(sourceFile), node.end, sourceFile);
 }
 
+function isThrow(node: ts.Node): boolean {
+    return isBlock(node)
+        ? node.statements.length === 1
+            ? isThrowStatement(node.statements[0])
+            : false
+        : isThrowStatement(node);
+}
+
 function diff(start: number, end: number, sourceFile: ts.SourceFile): number {
     return ts.getLineAndCharacterOfPosition(sourceFile, end).line
         - ts.getLineAndCharacterOfPosition(sourceFile, start).line

test/rules/early-exit/throwing-is-early-exit/test.ts.lint

@@ -0,0 +1,8 @@
+class Foo {
+    f(a) {
+        if (a === undefined) {
+            throw new Error("a is undefined");
+        }
+    }
+}
+

test/rules/early-exit/throwing-is-early-exit/tslint.json

@@ -0,0 +1,6 @@
+{
+  "rulesDirectory": "../../../../rules",
+    "rules": {
+        "early-exit": true
+    }
+}