From 8c4b344eb8e94ef3df4b146bc779503f62ca55f9 Mon Sep 17 00:00:00 2001
From: Matt Thalman <mthalman@microsoft.com>
Date: Thu, 26 Nov 2020 13:32:07 -0600
Subject: [PATCH] Fix parsing of empty line continuations for commands

---
 .../DockerfileModel.Tests/RunInstructionTests.cs   | 14 ++++++++++++++
 .../DockerfileModel.Tests/ShellFormCommandTests.cs | 14 ++++++++++++++
 src/DockerfileModel/DockerfileModel/ParseHelper.cs |  8 +++++---
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/src/DockerfileModel/DockerfileModel.Tests/RunInstructionTests.cs b/src/DockerfileModel/DockerfileModel.Tests/RunInstructionTests.cs
index 9f2efcb..063bc66 100644
--- a/src/DockerfileModel/DockerfileModel.Tests/RunInstructionTests.cs
+++ b/src/DockerfileModel/DockerfileModel.Tests/RunInstructionTests.cs
@@ -137,6 +137,20 @@ public static IEnumerable<object[]> ParseTestInput()
                     }
                 },
                 new RunInstructionParseTestScenario
+                {
+                    Text = "RUN `\n`\necho hello",
+                    EscapeChar = '`',
+                    TokenValidators = new Action<Token>[]
+                    {
+                        token => ValidateKeyword(token, "RUN"),
+                        token => ValidateWhitespace(token, " "),
+                        token => ValidateLineContinuation(token, '`', "\n"),
+                        token => ValidateLineContinuation(token, '`', "\n"),
+                        token => ValidateAggregate<ShellFormCommand>(token, "echo hello",
+                            token => ValidateLiteral(token, "echo hello"))
+                    }
+                },
+                new RunInstructionParseTestScenario
                 {
                     Text = "RUN echo `\n#test comment\nhello",
                     EscapeChar = '`',
diff --git a/src/DockerfileModel/DockerfileModel.Tests/ShellFormCommandTests.cs b/src/DockerfileModel/DockerfileModel.Tests/ShellFormCommandTests.cs
index f5ab3e2..ce3f2db 100644
--- a/src/DockerfileModel/DockerfileModel.Tests/ShellFormCommandTests.cs
+++ b/src/DockerfileModel/DockerfileModel.Tests/ShellFormCommandTests.cs
@@ -109,6 +109,20 @@ public static IEnumerable<object[]> ParseTestInput()
                     }
                 },
                 new ShellFormCommandParseTestScenario
+                {
+                    Text = "echo`\n  `\n  hello",
+                    EscapeChar = '`',
+                    TokenValidators = new Action<Token>[]
+                    {
+                        token => ValidateAggregate<LiteralToken>(token, "echo`\n  `\n  hello",
+                            token => ValidateString(token, "echo"),
+                            token => ValidateLineContinuation(token, '`', "\n"),
+                            token => ValidateString(token, "  "),
+                            token => ValidateLineContinuation(token, '`', "\n"),
+                            token => ValidateString(token, "  hello")),
+                    }
+                },
+                new ShellFormCommandParseTestScenario
                 {
                     Text = "ec`\nho `test",
                     EscapeChar = '`',
diff --git a/src/DockerfileModel/DockerfileModel/ParseHelper.cs b/src/DockerfileModel/DockerfileModel/ParseHelper.cs
index e22b928..07db6e2 100644
--- a/src/DockerfileModel/DockerfileModel/ParseHelper.cs
+++ b/src/DockerfileModel/DockerfileModel/ParseHelper.cs
@@ -308,9 +308,11 @@ public static Parser<IEnumerable<Token>> LiteralString(char escapeChar, IEnumera
         /// </summary>
         /// <param name="escapeChar">Escape character.</param>
         public static Parser<IEnumerable<Token>> ArgumentListAsLiteral(char escapeChar) =>
-            from literals in ArgTokens(
-                LiteralToken(escapeChar, Enumerable.Empty<char>()).AsEnumerable(),
-                escapeChar).Many()
+            from literals in
+                ArgTokens(
+                    from literal in LiteralToken(escapeChar, Enumerable.Empty<char>()).Optional()
+                    select new Token[] { literal.GetOrDefault() },
+                    escapeChar).Many()
             select CollapseLiteralTokens(literals.Flatten(), canContainVariables: false, escapeChar);
 
         /// <summary>