Evaluate rhs after string slices

.golangci.yml

@@ -64,3 +64,14 @@ linters:
     - whitespace
     # - wrapcheck
     # - wsl
+
+linters-settings:
+  depguard:
+    rules:
+      main:
+        files:
+          - $all
+          - "!$test"
+        allow:
+          - $gostd
+          - github.com/jmespath-community/go-jmespath

Makefile

@@ -21,6 +21,9 @@ build:
 test: build
 	go test -v ./...
 
+format:
+	gofumpt -l -w .
+
 check:
 	go vet ./...
 	staticcheck ./...
@@ -43,5 +46,6 @@ pprof-cpu:
 
 install-dev-cmds:
 	go install honnef.co/go/tools/cmd/staticcheck@latest
+	go install mvdan.cc/gofumpt@latest
 	go install golang.org/x/tools/cmd/stringer@latest
-	command -v golangci-lint || { curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $$(go env GOPATH)/bin v1.46.2; }
+	command -v golangci-lint || { curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $$(go env GOPATH)/bin v1.61.0; }

pkg/interpreter/interpreter.go

@@ -374,7 +374,13 @@ func (intr *treeInterpreter) execute(node parsing.ASTNode, value any, functionCa
 			}
 			stringType, ok := left.(string)
 			if allowString && ok {
-				return stringType, nil
+				// a projection is really a sub-expression in disguise
+				// we must evaluate the right hand expression
+				result, err := intr.Execute(node.Children[1], stringType)
+				if err != nil {
+					return nil, err
+				}
+				return result, nil
 			}
 			return nil, nil
 		}

pkg/interpreter/interpreter_test.go

@@ -193,6 +193,22 @@ func TestCanSupportSliceOfStructsWithFunctions(t *testing.T) {
 	assert.Equal(result.(float64), 2.0)
 }
 
+func TestCanSupportEvaluatingRightHandSideOfStringSlice(t *testing.T) {
+	assert := assert.New(t)
+	data := make(map[string]interface{})
+	result, err := search(t, "'foo'[:].length(@)", data)
+	assert.Nil(err)
+	assert.Equal(result.(float64), 3.0)
+}
+
+func TestErrEvaluatingRightHandSideOfStringSlice(t *testing.T) {
+	assert := assert.New(t)
+	data := make(map[string]interface{})
+	_, err := search(t, "'foo'[:].unknown(@)", data)
+	assert.NotNil(err)
+	assert.Equal("unknown function: unknown", err.Error())
+}
+
 func BenchmarkInterpretSingleFieldStruct(b *testing.B) {
 	assert := assert.New(b)
 	intr := NewInterpreter(nil, nil)