builder: Handle trailing \ appropriately.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Upstream-commit: 7fa449191ce9abc3e0a5261b66d8338948f66940
Component: engine

components/engine/builder/parser/parser.go

@@ -32,7 +32,7 @@ type Node struct {
 var (
 	dispatch                map[string]func(string) (*Node, map[string]bool, error)
 	TOKEN_WHITESPACE        = regexp.MustCompile(`[\t\v\f\r ]+`)
-	TOKEN_LINE_CONTINUATION = regexp.MustCompile(`\\$`)
+	TOKEN_LINE_CONTINUATION = regexp.MustCompile(`\\\s*$`)
 	TOKEN_COMMENT           = regexp.MustCompile(`^#.*$`)
 )
 

components/engine/builder/parser/testfiles/continueIndent/Dockerfile

@@ -14,6 +14,7 @@ RUN echo hello \
 goodbye\
 frog
 RUN echo hello  \  
+world
 RUN echo hi \
  \
  world \

components/engine/builder/parser/testfiles/continueIndent/result

@@ -3,7 +3,7 @@
 (run "echo hello    world")
 (run "echo hello  world")
 (run "echo hello goodbyefrog")
-(run "echo hello  \\")
+(run "echo hello  world")
 (run "echo hi   world  goodnight")
 (run "echo goodbyefrog")
 (run "echo goodbyefrog")