From ddd8f71dcc9439ee2ad1c6a18f95f2b884e34789 Mon Sep 17 00:00:00 2001
From: hadley <h.wickham@gmail.com>
Date: Thu, 28 Jun 2018 15:59:39 -0500
Subject: [PATCH] Improve md link parsing

By prohibiting [ inside of links; fixes #555.
---
 NEWS.md                                 |  3 +++
 R/markdown.R                            | 14 ++++++++++----
 tests/testthat/test-rd-markdown-links.R |  7 +++++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index e6059af24..88c10d5fb 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -108,6 +108,9 @@
       space (#628, @egnha).
   
     * `%` in inline code blocks is now automatically escaped (#640).
+    
+    * Parsing of markdown links has been tweaked to reduce false positives 
+      (#555)
 
 # roxygen2 6.0.1
 
diff --git a/R/markdown.R b/R/markdown.R
index 72f227283..01e24d392 100644
--- a/R/markdown.R
+++ b/R/markdown.R
@@ -278,10 +278,10 @@ add_linkrefs_to_md <- function(text) {
     regex(
       comments = TRUE,
       "
-        (?<=[^\\]]|^)        # must not be preceded by ]
-        \\[([^\\]]+)\\]      # match anything inside of []
-        (?:\\[([^\\]]+)\\])? # match optional second pair of []
-        (?=[^\\[]|$)         # must not be followed by [
+        (?<=[^\\]]|^)           # must not be preceded by ]
+        \\[([^\\]\\[]+)\\]      # match anything inside of []
+        (?:\\[([^\\]\\[]+)\\])? # match optional second pair of []
+        (?=[^\\[]|$)            # must not be followed by [
       "
     )
   )[[1]]
@@ -303,6 +303,12 @@ add_linkrefs_to_md <- function(text) {
   )
 }
 
+# Helper designed primarily for testing
+
+md_link_html <- function(x) {
+  commonmark::markdown_html(add_linkrefs_to_md(x))
+}
+
 #' Parse a MarkDown link, to see if we should create an Rd link
 #'
 #' See the table above.
diff --git a/tests/testthat/test-rd-markdown-links.R b/tests/testthat/test-rd-markdown-links.R
index 9e019d742..c95c70d96 100644
--- a/tests/testthat/test-rd-markdown-links.R
+++ b/tests/testthat/test-rd-markdown-links.R
@@ -24,6 +24,13 @@ test_that("proper link references are added", {
   }
 })
 
+test_that("can not have [ inside of link", {
+  expect_equal(
+    md_link_html("`[[`. [subset()]"),
+    "<p><code>[[</code>. <a href=\"R:subset()\">subset()</a></p>\n"
+  )
+})
+
 test_that("commonmark picks up the various link references", {
   cases <- list(
     c("foo [func()] bar",