Implement include parameters

README.md

@@ -33,8 +33,10 @@ This project is missing more functionality than it implements. It may accidental
     - [ ] Remaining Jekyll Liquid tags
     - [ ] Jekyll Liquid filters
   - [x] Includes
-    - [ ] parameters
     - [ ] `include_relative`
+    - [x] parameters
+      - [ ] variable parameters
+    - [ ] variables `{% include {{ expr }} %}`
   - [x] Permalinks
   - [ ] Pagination
   - [ ] Themes

liquid/tags.go

@@ -3,6 +3,8 @@ package liquid
 import (
 	"fmt"
 	"io"
+	"regexp"
+	"strings"
 
 	"github.com/osteele/liquid/chunks"
 )
@@ -18,9 +20,40 @@ func (e *LocalWrapperEngine) addJekyllTags() {
 			return err
 		}, nil
 	})
-	e.engine.DefineTag("include", func(filename string) (func(io.Writer, chunks.Context) error, error) {
+	e.engine.DefineTag("include", func(line string) (func(io.Writer, chunks.Context) error, error) {
+		// TODO escapes
+		includeLinePattern := regexp.MustCompile(`^\S+(?:\s+\S+=("[^"]+"|'[^']'|[^'"\s]+))*$`)
+		includeParamPattern := regexp.MustCompile(`\b(\S+)=("[^"]+"|'[^']'|[^'"\s]+)(?:\s|$)`)
+		if !includeLinePattern.MatchString(line) {
+			return nil, fmt.Errorf("parse error in include tag parameters")
+		}
+		filename := strings.Fields(line)[0]
+		type paramSpec struct {
+			value string
+			eval  bool
+		}
+		params := map[string]paramSpec{}
+		for _, m := range includeParamPattern.FindAllStringSubmatch(line, -1) {
+			k, v, eval := m[1], m[2], true
+			if strings.HasPrefix(v, `'`) || strings.HasPrefix(v, `"`) {
+				v, eval = v[1:len(v)-1], false
+			}
+			params[k] = paramSpec{v, eval}
+		}
 		return func(w io.Writer, ctx chunks.Context) error {
-			return e.includeTagHandler(filename, w, ctx.GetVariableMap())
+			include := map[string]interface{}{}
+			for k, v := range params {
+				if v.eval {
+					// TODO include parameter variables
+					panic(fmt.Errorf("include parameter variables aren't implemented"))
+				} else {
+					include[k] = v.value
+				}
+			}
+			bindings := ctx.GetVariableMap()
+			// TODO use a copy of this
+			bindings["include"] = include
+			return e.includeTagHandler(filename, w, bindings)
 		}, nil
 	})
 }