From 088dd9fc61af33d86fcb2f2d6a6a013050960368 Mon Sep 17 00:00:00 2001
From: "Benjamin E. Coe" <bencoe@gmail.com>
Date: Thu, 31 May 2018 16:18:21 -0700
Subject: [PATCH] feat: add support for optional catch binding (#175)

---
 .../src/instrumenter.js                       |  1 +
 .../src/read-coverage.js                      |  1 +
 .../test/specs/try.yaml                       | 26 +++++++++++++++++++
 .../test/util/guards.js                       |  4 +++
 4 files changed, 32 insertions(+)

diff --git a/packages/istanbul-lib-instrument/src/instrumenter.js b/packages/istanbul-lib-instrument/src/instrumenter.js
index d6e7655b..d563799c 100644
--- a/packages/istanbul-lib-instrument/src/instrumenter.js
+++ b/packages/istanbul-lib-instrument/src/instrumenter.js
@@ -87,6 +87,7 @@ class Instrumenter {
               'asyncGenerators',
               'dynamicImport',
               'objectRestSpread',
+              'optionalCatchBinding',
               'flow',
               'jsx'
             ]
diff --git a/packages/istanbul-lib-instrument/src/read-coverage.js b/packages/istanbul-lib-instrument/src/read-coverage.js
index a4a3fb6f..5e95f7c3 100644
--- a/packages/istanbul-lib-instrument/src/read-coverage.js
+++ b/packages/istanbul-lib-instrument/src/read-coverage.js
@@ -18,6 +18,7 @@ export default function readInitialCoverage (code) {
           'asyncGenerators',
           'dynamicImport',
           'objectRestSpread',
+          'optionalCatchBinding',
           'flow',
           'jsx'
         ]
diff --git a/packages/istanbul-lib-instrument/test/specs/try.yaml b/packages/istanbul-lib-instrument/test/specs/try.yaml
index 0acdf30a..101b9839 100644
--- a/packages/istanbul-lib-instrument/test/specs/try.yaml
+++ b/packages/istanbul-lib-instrument/test/specs/try.yaml
@@ -23,3 +23,29 @@ tests:
     lines: {'1': 1, '2': 1, '3': 0, '5': 1, '7': 1}
     branches: {'0': [1, 0]}
     statements: {'0': 1, '1': 1, '2': 1, '3': 0, '4': 1, '5': 1}
+---
+name: optional catch binding
+guard: isOptionalCatchBindingAvailable
+code: |
+  try {
+     if (args[0] === "X") { throw "foo"; }
+     output = args[0];
+  } catch {
+     output="Y";
+  } finally {
+     output += 1;
+  }
+tests:
+  - name: happy path
+    args: [1]
+    out: 2
+    lines: {'1': 1, '2': 1, '3': 1, '5': 0, '7': 1}
+    branches: {'0': [0, 1]}
+    statements: {'0': 1, '1': 1, '2': 0, '3': 1, '4': 0, '5': 1}
+
+  - name: sad path
+    args: [X]
+    out: Y1
+    lines: {'1': 1, '2': 1, '3': 0, '5': 1, '7': 1}
+    branches: {'0': [1, 0]}
+    statements: {'0': 1, '1': 1, '2': 1, '3': 0, '4': 1, '5': 1}
diff --git a/packages/istanbul-lib-instrument/test/util/guards.js b/packages/istanbul-lib-instrument/test/util/guards.js
index 927fa167..38c67b2a 100644
--- a/packages/istanbul-lib-instrument/test/util/guards.js
+++ b/packages/istanbul-lib-instrument/test/util/guards.js
@@ -42,6 +42,10 @@ export function isObjectFreezeAvailable() {
     }
 }
 
+export function isOptionalCatchBindingAvailable () {
+    return tryThis('try {} catch {}');
+}
+
 export function isImportAvailable() {
     return tryThis('import fs from "fs"', 'import', true);
 }