feat: conditionally include error handling in generated client code templates

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/cmd/ndpgen/internal/generator_test.go

@@ -586,6 +586,101 @@ var _ = Describe("Generator", func() {
 		})
 	})
 
+	Describe("GenerateClientGo", func() {
+		It("should include errors import when service has methods with errors", func() {
+			svc := Service{
+				Name:       "Cache",
+				Permission: "cache",
+				Interface:  "CacheService",
+				Methods: []Method{
+					{
+						Name:     "Get",
+						HasError: true,
+						Params:   []Param{NewParam("key", "string")},
+						Returns:  []Param{NewParam("value", "string")},
+					},
+				},
+			}
+
+			code, err := GenerateClientGo(svc, "host")
+			Expect(err).NotTo(HaveOccurred())
+
+			// Verify the code is valid Go (can't actually compile without wasip1)
+			codeStr := string(code)
+
+			// Check for errors import when methods have errors
+			Expect(codeStr).To(ContainSubstring(`"errors"`))
+			Expect(codeStr).To(ContainSubstring("errors.New"))
+		})
+
+		It("should not include errors import when service has no methods with errors", func() {
+			svc := Service{
+				Name:       "Config",
+				Permission: "config",
+				Interface:  "ConfigService",
+				Methods: []Method{
+					{
+						Name:     "Get",
+						HasError: false,
+						Params:   []Param{NewParam("key", "string")},
+						Returns:  []Param{NewParam("value", "string"), NewParam("exists", "bool")},
+					},
+					{
+						Name:     "List",
+						HasError: false,
+						Params:   []Param{NewParam("prefix", "string")},
+						Returns:  []Param{NewParam("keys", "[]string")},
+					},
+				},
+			}
+
+			code, err := GenerateClientGo(svc, "host")
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Check that errors is NOT imported when no methods have errors
+			Expect(codeStr).NotTo(ContainSubstring(`"errors"`))
+			Expect(codeStr).NotTo(ContainSubstring("errors.New"))
+		})
+
+		It("should generate valid Go code structure", func() {
+			svc := Service{
+				Name:       "SubsonicAPI",
+				Permission: "subsonicapi",
+				Interface:  "SubsonicAPIService",
+				Methods: []Method{
+					{
+						Name:     "Call",
+						HasError: true,
+						Params:   []Param{NewParam("uri", "string")},
+						Returns:  []Param{NewParam("response", "string")},
+					},
+				},
+			}
+
+			code, err := GenerateClientGo(svc, "host")
+			Expect(err).NotTo(HaveOccurred())
+
+			codeStr := string(code)
+
+			// Check for generated header
+			Expect(codeStr).To(ContainSubstring("Code generated by ndpgen. DO NOT EDIT."))
+
+			// Check for build tag
+			Expect(codeStr).To(ContainSubstring("//go:build wasip1"))
+
+			// Check for package declaration
+			Expect(codeStr).To(ContainSubstring("package host"))
+
+			// Check for wasmimport directive
+			Expect(codeStr).To(ContainSubstring("//go:wasmimport extism:host/user"))
+
+			// Check for PDK import
+			Expect(codeStr).To(ContainSubstring("github.com/navidrome/navidrome/plugins/pdk/go/pdk"))
+		})
+	})
+
 	Describe("GenerateClientGoStub", func() {
 		It("should generate valid mock code with testify/mock", func() {
 			svc := Service{

plugins/cmd/ndpgen/internal/templates/client.go.tmpl

@@ -9,7 +9,9 @@ package {{.Package}}
 
 import (
 	"encoding/json"
+{{- if .Service.HasErrors}}
 	"errors"
+{{- end}}
 
 	"github.com/navidrome/navidrome/plugins/pdk/go/pdk"
 )
@@ -53,7 +55,9 @@ type {{responseType .}} struct {
 {{- range .Returns}}
 	{{title .Name}} {{.Type}} `json:"{{.JSONName}},omitempty"`
 {{- end}}
+{{- if .HasError}}
 	Error string `json:"error,omitempty"`
+{{- end}}
 }
 {{- end}}
 {{- end}}

plugins/cmd/ndpgen/internal/templates/client.py.tmpl

@@ -80,10 +80,11 @@ def {{pythonFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.PythonNam
     response_offset = _{{exportName .}}(request_mem.offset)
     response_mem = extism.memory.find(response_offset)
     response = json.loads(extism.memory.string(response_mem))
-
+{{if .HasError}}
     if response.get("error"):
         raise HostFunctionError(response["error"])
-{{if .NeedsResultClass}}
+{{end}}
+{{- if .NeedsResultClass}}
     return {{pythonResultType .}}(
 {{- range .Returns}}
         {{.PythonName}}=response.get("{{.JSONName}}"{{pythonDefault .}}),

plugins/cmd/ndpgen/internal/templates/client.rs.tmpl

@@ -41,8 +41,10 @@ struct {{responseType .}} {
     #[serde(default)]
     {{.RustName}}: {{rustType .}},
 {{- end}}
+{{- if .HasError}}
     #[serde(default)]
     error: Option<String>,
+{{- end}}
 }
 {{- end}}
 
@@ -88,11 +90,12 @@ pub fn {{rustFunc .}}({{range $i, $p := .Params}}{{if $i}}, {{end}}{{$p.RustName
         {{exportName .}}(Json(serde_json::json!({})))?
 {{- end}}
     };
-
+{{if .HasError}}
     if let Some(err) = response.0.error {
         return Err(Error::msg(err));
     }
-{{if eq (len .Returns) 0}}
+{{end}}
+{{- if eq (len .Returns) 0}}
     Ok(())
 {{- else if eq (len .Returns) 1}}
     Ok(response.0.{{(index .Returns 0).RustName}})

plugins/cmd/ndpgen/internal/templates/host.go.tmpl

@@ -26,7 +26,9 @@ type {{responseType .}} struct {
 {{- range .Returns}}
 	{{title .Name}} {{.Type}} `json:"{{.JSONName}},omitempty"`
 {{- end}}
+{{- if .HasError}}
 	Error string `json:"error,omitempty"`
+{{- end}}
 }
 {{end}}
 

plugins/cmd/ndpgen/internal/types.go

@@ -163,6 +163,16 @@ func (s Service) KnownStructs() map[string]bool {
 	return result
 }
 
+// HasErrors returns true if any method in the service returns an error.
+func (s Service) HasErrors() bool {
+	for _, m := range s.Methods {
+		if m.HasError {
+			return true
+		}
+	}
+	return false
+}
+
 // Method represents a host function method within a service.
 type Method struct {
 	Name       string  // Go method name (e.g., "Call")

plugins/cmd/ndpgen/testdata/counter_client_expected.go.txt

@@ -9,7 +9,6 @@ package ndhost
 
 import (
 	"encoding/json"
-	"errors"
 
 	"github.com/navidrome/navidrome/plugins/pdk/go/pdk"
 )
@@ -24,8 +23,7 @@ type counterCountRequest struct {
 }
 
 type counterCountResponse struct {
-	Value int32  `json:"value,omitempty"`
-	Error string `json:"error,omitempty"`
+	Value int32 `json:"value,omitempty"`
 }
 
 // CounterCount calls the counter_count host function.

plugins/cmd/ndpgen/testdata/counter_client_expected.py

@@ -46,7 +46,4 @@ def counter_count(name: str) -> int:
     response_mem = extism.memory.find(response_offset)
     response = json.loads(extism.memory.string(response_mem))
 
-    if response.get("error"):
-        raise HostFunctionError(response["error"])
-
     return response.get("value", 0)

plugins/cmd/ndpgen/testdata/counter_client_expected.rs

@@ -17,8 +17,6 @@ struct CounterCountRequest {
 struct CounterCountResponse {
     #[serde(default)]
     value: i32,
-    #[serde(default)]
-    error: Option<String>,
 }
 
 #[host_fn]
@@ -43,9 +41,5 @@ pub fn count(name: &str) -> Result<i32, Error> {
         }))?
     };
 
-    if let Some(err) = response.0.error {
-        return Err(Error::msg(err));
-    }
-
     Ok(response.0.value)
 }

plugins/cmd/ndpgen/testdata/counter_expected.go.txt

@@ -16,8 +16,7 @@ type CounterCountRequest struct {
 
 // CounterCountResponse is the response type for Counter.Count.
 type CounterCountResponse struct {
-	Value int32  `json:"value,omitempty"`
-	Error string `json:"error,omitempty"`
+	Value int32 `json:"value,omitempty"`
 }
 
 // RegisterCounterHostFunctions registers Counter service host functions.