1 files changed, 185 insertions, 0 deletions
diff --git a/pkg/jobparser/evaluator.go b/pkg/jobparser/evaluator.go
new file mode 100644
index 0000000..80a1397
--- /dev/null
+++ b/pkg/jobparser/evaluator.go
@@ -0,0 +1,185 @@
+package jobparser
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/nektos/act/pkg/exprparser"
+	"gopkg.in/yaml.v3"
+)
+
+// ExpressionEvaluator is copied from runner.expressionEvaluator,
+// to avoid unnecessary dependencies
+type ExpressionEvaluator struct {
+	interpreter exprparser.Interpreter
+}
+
+func NewExpressionEvaluator(interpreter exprparser.Interpreter) *ExpressionEvaluator {
+	return &ExpressionEvaluator{interpreter: interpreter}
+}
+
+func (ee ExpressionEvaluator) evaluate(in string, defaultStatusCheck exprparser.DefaultStatusCheck) (interface{}, error) {
+	evaluated, err := ee.interpreter.Evaluate(in, defaultStatusCheck)
+
+	return evaluated, err
+}
+
+func (ee ExpressionEvaluator) evaluateScalarYamlNode(node *yaml.Node) error {
+	var in string
+	if err := node.Decode(&in); err != nil {
+		return err
+	}
+	if !strings.Contains(in, "${{") || !strings.Contains(in, "}}") {
+		return nil
+	}
+	expr, _ := rewriteSubExpression(in, false)
+	res, err := ee.evaluate(expr, exprparser.DefaultStatusCheckNone)
+	if err != nil {
+		return err
+	}
+	return node.Encode(res)
+}
+
+func (ee ExpressionEvaluator) evaluateMappingYamlNode(node *yaml.Node) error {
+	// GitHub has this undocumented feature to merge maps, called insert directive
+	insertDirective := regexp.MustCompile(`\${{\s*insert\s*}}`)
+	for i := 0; i < len(node.Content)/2; {
+		k := node.Content[i*2]
+		v := node.Content[i*2+1]
+		if err := ee.EvaluateYamlNode(v); err != nil {
+			return err
+		}
+		var sk string
+		// Merge the nested map of the insert directive
+		if k.Decode(&sk) == nil && insertDirective.MatchString(sk) {
+			node.Content = append(append(node.Content[:i*2], v.Content...), node.Content[(i+1)*2:]...)
+			i += len(v.Content) / 2
+		} else {
+			if err := ee.EvaluateYamlNode(k); err != nil {
+				return err
+			}
+			i++
+		}
+	}
+	return nil
+}
+
+func (ee ExpressionEvaluator) evaluateSequenceYamlNode(node *yaml.Node) error {
+	for i := 0; i < len(node.Content); {
+		v := node.Content[i]
+		// Preserve nested sequences
+		wasseq := v.Kind == yaml.SequenceNode
+		if err := ee.EvaluateYamlNode(v); err != nil {
+			return err
+		}
+		// GitHub has this undocumented feature to merge sequences / arrays
+		// We have a nested sequence via evaluation, merge the arrays
+		if v.Kind == yaml.SequenceNode && !wasseq {
+			node.Content = append(append(node.Content[:i], v.Content...), node.Content[i+1:]...)
+			i += len(v.Content)
+		} else {
+			i++
+		}
+	}
+	return nil
+}
+
+func (ee ExpressionEvaluator) EvaluateYamlNode(node *yaml.Node) error {
+	switch node.Kind {
+	case yaml.ScalarNode:
+		return ee.evaluateScalarYamlNode(node)
+	case yaml.MappingNode:
+		return ee.evaluateMappingYamlNode(node)
+	case yaml.SequenceNode:
+		return ee.evaluateSequenceYamlNode(node)
+	default:
+		return nil
+	}
+}
+
+func (ee ExpressionEvaluator) Interpolate(in string) string {
+	if !strings.Contains(in, "${{") || !strings.Contains(in, "}}") {
+		return in
+	}
+
+	expr, _ := rewriteSubExpression(in, true)
+	evaluated, err := ee.evaluate(expr, exprparser.DefaultStatusCheckNone)
+	if err != nil {
+		return ""
+	}
+
+	value, ok := evaluated.(string)
+	if !ok {
+		panic(fmt.Sprintf("Expression %s did not evaluate to a string", expr))
+	}
+
+	return value
+}
+
+func escapeFormatString(in string) string {
+	return strings.ReplaceAll(strings.ReplaceAll(in, "{", "{{"), "}", "}}")
+}
+
+func rewriteSubExpression(in string, forceFormat bool) (string, error) {
+	if !strings.Contains(in, "${{") || !strings.Contains(in, "}}") {
+		return in, nil
+	}
+
+	strPattern := regexp.MustCompile("(?:''|[^'])*'")
+	pos := 0
+	exprStart := -1
+	strStart := -1
+	var results []string
+	formatOut := ""
+	for pos < len(in) {
+		if strStart > -1 {
+			matches := strPattern.FindStringIndex(in[pos:])
+			if matches == nil {
+				panic("unclosed string.")
+			}
+
+			strStart = -1
+			pos += matches[1]
+		} else if exprStart > -1 {
+			exprEnd := strings.Index(in[pos:], "}}")
+			strStart = strings.Index(in[pos:], "'")
+
+			if exprEnd > -1 && strStart > -1 {
+				if exprEnd < strStart {
+					strStart = -1
+				} else {
+					exprEnd = -1
+				}
+			}
+
+			if exprEnd > -1 {
+				formatOut += fmt.Sprintf("{%d}", len(results))
+				results = append(results, strings.TrimSpace(in[exprStart:pos+exprEnd]))
+				pos += exprEnd + 2
+				exprStart = -1
+			} else if strStart > -1 {
+				pos += strStart + 1
+			} else {
+				panic("unclosed expression.")
+			}
+		} else {
+			exprStart = strings.Index(in[pos:], "${{")
+			if exprStart != -1 {
+				formatOut += escapeFormatString(in[pos : pos+exprStart])
+				exprStart = pos + exprStart + 3
+				pos = exprStart
+			} else {
+				formatOut += escapeFormatString(in[pos:])
+				pos = len(in)
+			}
+		}
+	}
+
+	if len(results) == 1 && formatOut == "{0}" && !forceFormat {
+		return in, nil
+	}
+
+	out := fmt.Sprintf("format('%s', %s)", strings.ReplaceAll(formatOut, "'", "''"), strings.Join(results, ", "))
+	return out, nil
+}