From 362d8e2a9fb9ced3cca91098040c8acd39197d85 Mon Sep 17 00:00:00 2001
From: Dillon Kearns <dillon@dillonkearns.com>
Date: Tue, 1 Jun 2021 09:39:12 -0700
Subject: [PATCH 1/3] Add fuzz tester to catch cases where parser fails.

---
 tests/ParserRecoveryTests.elm | 68 +++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 tests/ParserRecoveryTests.elm

diff --git a/tests/ParserRecoveryTests.elm b/tests/ParserRecoveryTests.elm
new file mode 100644
index 0000000..007ea46
--- /dev/null
+++ b/tests/ParserRecoveryTests.elm
@@ -0,0 +1,68 @@
+module ParserRecoveryTests exposing (suite)
+
+import Expect exposing (Expectation)
+import Fuzz
+import Markdown.Block as Block exposing (..)
+import Markdown.Parser as Markdown exposing (..)
+import Parser
+import Parser.Advanced as Advanced exposing ((|.), (|=))
+import Test exposing (..)
+
+
+type alias Parser a =
+    Advanced.Parser String Parser.Problem a
+
+
+parse : String -> Result (List (Advanced.DeadEnd String Parser.Problem)) (List Block)
+parse markdown =
+    markdown
+        |> Markdown.parse
+
+
+suite : Test
+suite =
+    describe "parser errors all have fallbacks so parsing always succeeds"
+        [ fuzz Fuzz.string "random strings are parseable" <|
+            \randomString ->
+                randomString
+                    |> Markdown.parse
+                    |> Expect.ok
+        ]
+
+
+expectOk : List Block -> String -> Expectation
+expectOk expected input =
+    case input |> parse of
+        Ok actual ->
+            actual
+                |> Expect.equal expected
+
+        Err error ->
+            Expect.fail (Debug.toString error)
+
+
+plainListItem : String -> Block.ListItem Block.Inline
+plainListItem body =
+    Block.ListItem Block.NoTask [ Block.Text body ]
+
+
+unstyledText : String -> List Inline
+unstyledText body =
+    [ Block.Text body ]
+
+
+emphasisText : String -> List Inline
+emphasisText body =
+    [ Block.Emphasis <|
+        [ Block.Text body ]
+    ]
+
+
+parserError : String -> Expect.Expectation
+parserError markdown =
+    case parse markdown of
+        Ok _ ->
+            Expect.fail "Expected a parser failure!"
+
+        Err _ ->
+            Expect.pass

From fd67e4403f6fc34587dc2ca4119d6afd9f719f7b Mon Sep 17 00:00:00 2001
From: Dillon Kearns <dillon@dillonkearns.com>
Date: Tue, 1 Jun 2021 10:14:00 -0700
Subject: [PATCH 2/3] Add another failing test case.

---
 tests/ParserRecoveryTests.elm | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tests/ParserRecoveryTests.elm b/tests/ParserRecoveryTests.elm
index 007ea46..1814df3 100644
--- a/tests/ParserRecoveryTests.elm
+++ b/tests/ParserRecoveryTests.elm
@@ -3,6 +3,7 @@ module ParserRecoveryTests exposing (suite)
 import Expect exposing (Expectation)
 import Fuzz
 import Markdown.Block as Block exposing (..)
+import Markdown.Inline
 import Markdown.Parser as Markdown exposing (..)
 import Parser
 import Parser.Advanced as Advanced exposing ((|.), (|=))
@@ -27,6 +28,18 @@ suite =
                 randomString
                     |> Markdown.parse
                     |> Expect.ok
+        , test "recover from invalid html" <|
+            \() ->
+                "<no-closing-tag maybe this can just be rendered as a regular paragraph and not as HTML"
+                    |> Markdown.parse
+                    |> Expect.equal
+                        (Ok
+                            [ Block.Paragraph
+                                [ Block.Text
+                                    "<no-closing-tag maybe this can just be rendered as a regular paragraph and not as HTML"
+                                ]
+                            ]
+                        )
         ]
 
 

From e0d939f4b5b17abdce9105addef93bb4d794afa5 Mon Sep 17 00:00:00 2001
From: Dillon Kearns <dillon@dillonkearns.com>
Date: Tue, 1 Jun 2021 10:20:46 -0700
Subject: [PATCH 3/3] Add a passing test case for <| and << fallbacks.

---
 tests/ParserRecoveryTests.elm | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/ParserRecoveryTests.elm b/tests/ParserRecoveryTests.elm
index 1814df3..765eadd 100644
--- a/tests/ParserRecoveryTests.elm
+++ b/tests/ParserRecoveryTests.elm
@@ -40,6 +40,18 @@ suite =
                                 ]
                             ]
                         )
+        , test "<< is treated as regular text, not HTML" <|
+            \() ->
+                "In Elm, there are two ways to pipe: <| or <<"
+                    |> Markdown.parse
+                    |> Expect.equal
+                        (Ok
+                            [ Block.Paragraph
+                                [ Block.Text
+                                    "In Elm, there are two ways to pipe: <| or <<"
+                                ]
+                            ]
+                        )
         ]