dockerfile: implement additional expansions

Signed-off-by: Hank Donnay <hdonnay@redhat.com>

Author: hdonnay

rhel/dockerfile/generate.go

@@ -0,0 +1,5 @@
+package dockerfile
+
+//go:generate -command stringer go run golang.org/x/tools/cmd/stringer
+//go:generate stringer -type itemKind
+//go:generate stringer -type varExpand -linecomment

rhel/dockerfile/lex.go

@@ -58,9 +58,6 @@ type item struct {
 
 type itemKind int
 
-//go:generate -command stringer go run golang.org/x/tools/cmd/stringer
-//go:generate stringer -type itemKind
-
 const (
 	itemError itemKind = iota
 	itemComment

rhel/dockerfile/testdata/Colon.txtar

@@ -0,0 +1,3 @@
+error: dockerfile: bad expansion of "error": rogue colon
+-- Dockerfile --
+LABEL a ${error::}

rhel/dockerfile/testdata/Default.txtar

@@ -0,0 +1,15 @@
+-- Dockerfile --
+LABEL a ${unset}
+LABEL b ${unset=set}
+LABEL c ${unset}
+
+LABEL null=
+LABEL d ${null:=reset}
+-- Want --
+{
+  "a": "",
+  "b": "set",
+  "c": "set",
+  "d": "reset",
+  "null": ""
+}

rhel/dockerfile/testdata/Error.txtar

@@ -0,0 +1,3 @@
+error: dockerfile: bad expansion of "unset": should error (error if unset or null)
+-- Dockerfile --
+LABEL a ${unset:?should error}

rhel/dockerfile/testdata/Quoting.txtar

@@ -0,0 +1,11 @@
+-- Dockerfile --
+ARG a=\"
+ARG a=\'
+ARG a=\\
+ARG a=\b
+LABEL s='single\' quote: \\\b' d="double\" quote: \\\b\e"
+-- Want --
+{
+  "s": "single' quote: \\\\b",
+  "d": "double\" quote: \\\b\\e"
+}

rhel/dockerfile/testdata/Vars.txtar

@@ -0,0 +1,37 @@
+-- Dockerfile --
+ARG null=''
+LABEL dash_a ${unset-default}
+LABEL dash_b ${unset:-default}
+LABEL dash_c ${null-default}
+LABEL dash_d ${null:-default}
+LABEL plus_a ${unset+default}
+LABEL plus_b ${unset:+default}
+LABEL plus_c ${null+default}
+LABEL plus_d ${null:+default}
+
+ARG var=some-pattern.
+LABEL prefix ${var#*e}
+LABEL greedyprefix ${var##*e}
+LABEL suffix ${var%e*.}
+LABEL greedysuffix ${var%%e*.}
+LABEL singlechar ${var%?}
+LABEL greedysinglechar ${var%%?}
+LABEL noreplace ${var#\?}
+-- Want --
+{
+  "dash_a": "default",
+  "dash_b": "default",
+  "dash_c": "",
+  "dash_d": "default",
+  "plus_a": "",
+  "plus_b": "",
+  "plus_c": "default",
+  "plus_d": "",
+  "prefix": "-pattern.",
+  "greedyprefix": "rn.",
+  "suffix": "some-patt",
+  "greedysuffix": "som",
+  "singlechar": "some-pattern",
+  "greedysinglechar": "some-pattern",
+  "noreplace": "some-pattern."
+}