caddyfile: Implement variadics for import args placeholders (#5249)

* implement variadic placeholders
imported snippets reflect actual lines in file

* add import directive line number for imported snippets
add tests for parsing

* add realfile field to help debug import cycle detection.

* use file field to reflect import chain

* Switch syntax, deprecate old syntax, refactoring

- Moved the import args handling to a separate file
- Using {args[0:1]} syntax now
- Deprecate {args.*} syntax
- Use a replacer map for better control over the parsing
- Add plenty of warnings when invalid placeholders are detected
- Renaming variables, cleanup comments for readability
- More tests to cover edgecases I could think of
- Minor cleanup to snippet tracking in tokens, drop a redundant boolean field in tokens

---------

Co-authored-by: Francis Lavoie <lavofr@gmail.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/caddyconfig/caddyfile/parse_test.go b/caddyconfig/caddyfile/parse_test.go
index 4d18cc4..ad8683b 100644
--- a/caddyconfig/caddyfile/parse_test.go
+++ b/caddyconfig/caddyfile/parse_test.go
@@ -21,6 +21,88 @@ import (
 	"testing"
 )
 
+func TestParseVariadic(t *testing.T) {
+	var args = make([]string, 10)
+	for i, tc := range []struct {
+		input  string
+		result bool
+	}{
+		{
+			input:  "",
+			result: false,
+		},
+		{
+			input:  "{args[1",
+			result: false,
+		},
+		{
+			input:  "1]}",
+			result: false,
+		},
+		{
+			input:  "{args[:]}aaaaa",
+			result: false,
+		},
+		{
+			input:  "aaaaa{args[:]}",
+			result: false,
+		},
+		{
+			input:  "{args.}",
+			result: false,
+		},
+		{
+			input:  "{args.1}",
+			result: false,
+		},
+		{
+			input:  "{args[]}",
+			result: false,
+		},
+		{
+			input:  "{args[:]}",
+			result: true,
+		},
+		{
+			input:  "{args[:]}",
+			result: true,
+		},
+		{
+			input:  "{args[0:]}",
+			result: true,
+		},
+		{
+			input:  "{args[:0]}",
+			result: true,
+		},
+		{
+			input:  "{args[-1:]}",
+			result: false,
+		},
+		{
+			input:  "{args[:11]}",
+			result: false,
+		},
+		{
+			input:  "{args[10:0]}",
+			result: false,
+		},
+		{
+			input:  "{args[0:10]}",
+			result: true,
+		},
+	} {
+		token := Token{
+			File: "test",
+			Line: 1,
+			Text: tc.input,
+		}
+		if v, _, _ := parseVariadic(token, len(args)); v != tc.result {
+			t.Errorf("Test %d error expectation failed Expected: %t, got %t", i, tc.result, v)
+		}
+	}
+}
+
 func TestAllTokens(t *testing.T) {
 	input := []byte("a b c\nd e")
 	expected := []string{"a", "b", "c", "d", "e"}