From dd6e490a8ed499a362c6fe692155c7eba4732740 Mon Sep 17 00:00:00 2001
From: Eljees <3.14hell@gmail.com>
Date: Thu, 6 Aug 2026 20:44:17 +0300
Subject: [PATCH] parser: keep the newline that ends a heredoc terminator line

The heredoc terminator consumed the line break that follows the marker,
so the top level parser had nothing left to accept as the separator
before the next instruction. A comment or an instruction placed directly
after a heredoc failed to parse, while an empty line or a leading space
made the error go away.

Stop at the marker and only look ahead for the newline. The delimiter of
an empty heredoc has the same shape and is fixed the same way.

closes #99
related-to: hadolint/hadolint#960

Signed-off-by: Eljees <3.14hell@gmail.com>
---
 src/Language/Docker/Parser/Prelude.hs |  7 +++++--
 test/Language/Docker/ParseCopySpec.hs | 20 ++++++++++++++++++++
 test/Language/Docker/ParseRunSpec.hs  | 24 ++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/src/Language/Docker/Parser/Prelude.hs b/src/Language/Docker/Parser/Prelude.hs
index 1ca7bf9..3334173 100644
--- a/src/Language/Docker/Parser/Prelude.hs
+++ b/src/Language/Docker/Parser/Prelude.hs
@@ -202,8 +202,11 @@ heredocContent marker = do
     termination :: Parser Text
     termination = try terEOL <|> terEOF
 
+    -- The line break that follows the terminating marker is not part of the
+    -- heredoc: it is the line break that separates this instruction from
+    -- whatever comes next, so it is left for the caller to consume.
     terEOL :: Parser Text
-    terEOL = string $ "\n" <> marker <> "\n"
+    terEOL = string ("\n" <> marker) <* lookAhead (char '\n')
 
     terEOF :: Parser Text
     terEOF = do
@@ -215,7 +218,7 @@ heredocContent marker = do
     delimiter = try delEOL <|> delEOF
 
     delEOL :: Parser Text
-    delEOL = string $ marker <> "\n"
+    delEOL = string marker <* lookAhead (char '\n')
 
     delEOF :: Parser Text
     delEOF = do
diff --git a/test/Language/Docker/ParseCopySpec.hs b/test/Language/Docker/ParseCopySpec.hs
index 25aeb49..dd6c3a1 100644
--- a/test/Language/Docker/ParseCopySpec.hs
+++ b/test/Language/Docker/ParseCopySpec.hs
@@ -314,3 +314,23 @@ spec = do
                   ( CopyArgs [ SourcePath "FOO" ] ( TargetPath "/target" ) )
                   def
               ]
+    it "heredoc followed by another instruction" $
+      let file = Text.unlines ["COPY <<EOF /target", "content", "EOF", "COPY a b"]
+       in assertAst
+            file
+              [ Copy
+                  ( CopyArgs [ SourcePath "EOF" ] ( TargetPath "/target" ) )
+                  def,
+                Copy
+                  ( CopyArgs [ SourcePath "a" ] ( TargetPath "b" ) )
+                  def
+              ]
+    it "empty heredoc followed by a comment" $
+      let file = Text.unlines ["COPY <<EOF /target", "EOF", "# comment"]
+       in assertAst
+            file
+              [ Copy
+                  ( CopyArgs [ SourcePath "EOF" ] ( TargetPath "/target" ) )
+                  def,
+                Comment " comment"
+              ]
diff --git a/test/Language/Docker/ParseRunSpec.hs b/test/Language/Docker/ParseRunSpec.hs
index ea49256..0f4a067 100644
--- a/test/Language/Docker/ParseRunSpec.hs
+++ b/test/Language/Docker/ParseRunSpec.hs
@@ -567,6 +567,30 @@ spec = do
       let file = "RUN <<EOF\nEOF"
           flags = def { security = Nothing }
        in assertAst file [ Run $ RunArgs (ArgumentsText "") flags ]
+    it "heredoc followed by a comment" $
+      let file = Text.unlines [ "RUN <<EOF", "echo foo", "EOF", "# comment" ]
+          flags = def { security = Nothing }
+       in assertAst
+            file
+            [ Run $ RunArgs (ArgumentsText "echo foo") flags,
+              Comment " comment"
+            ]
+    it "heredoc followed by another instruction" $
+      let file = Text.unlines [ "RUN <<EOF", "echo foo", "EOF", "RUN echo bar" ]
+          flags = def { security = Nothing }
+       in assertAst
+            file
+            [ Run $ RunArgs (ArgumentsText "echo foo") flags,
+              Run $ RunArgs (ArgumentsText "echo bar") flags
+            ]
+    it "empty heredoc followed by a comment" $
+      let file = Text.unlines [ "RUN <<EOF", "EOF", "# comment" ]
+          flags = def { security = Nothing }
+       in assertAst
+            file
+            [ Run $ RunArgs (ArgumentsText "") flags,
+              Comment " comment"
+            ]
     it "evil heredoc" $
       let file = Text.unlines [ "RUN <<EOF foo", "bar EOF", "EOF"]
           flags = def { security = Nothing }