test(e2e): generated clients against a validating mock and a FastAPI backend

CLAUDE.md

@@ -14,6 +14,7 @@ make lint               # golangci-lint, config in .golangci.yml — must be cle
 make fmt                # gofumpt -w .
 make cover              # coverage.out + per-function summary
 make regress REF=master # generated output, working tree vs a git ref
+make e2e                # generated clients against a mock and FastAPI (testdata/e2e)
 go test ./internal/parser -run TestName
 ```
 
@@ -33,6 +34,7 @@ go.yaml.in/yaml/v3. No cgo.
 | `internal/codegen`              | the `Codegen*` structs templates render; fields mirror the Java originals   |
 | `internal/gen`                  | the pipeline: load spec → parse → render models, apis, supporting files     |
 | `internal/generator`            | `CodegenConfig` and the language configs, `typescript/`, `dart/`, `golang/` |
+| `internal/e2e`                  | end-to-end tests: mock server, runners, scenarios in `testdata/e2e`         |
 | `internal/template`             | the Mustache engine: partials, lambdas, struct-to-map via json              |
 | `internal/config`               | generator options and their config-file keys                                |
 | `internal/update`               | release check, verified download, self-update                               |

Makefile

@@ -1,4 +1,4 @@
-.PHONY: help test cover cover-html lint fmt vet build install clean tidy update samples-dart-fetch samples-go-fetch regress all
+.PHONY: help test cover cover-html lint fmt vet build install clean tidy update samples-dart-fetch samples-go-fetch regress e2e e2e-update all
 
 GOFUMPT ?= go run mvdan.cc/gofumpt@v0.12.0
 GOLANGCI ?= go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.13.0
@@ -19,6 +19,14 @@ test:
 	go vet ./...
 	go test -race ./...
 
+## e2e: generated clients against a validating mock and the FastAPI backend (needs uv), testdata/e2e
+e2e:
+	E2E=1 go test -count=1 -v ./internal/e2e
+
+## e2e-update: e2e, rewriting the snapshot of the backend's spec
+e2e-update:
+	E2E=1 E2E_UPDATE=1 go test -count=1 -v ./internal/e2e
+
 ## cover: Run tests with coverage
 cover:
 	go test -v -race -coverprofile=coverage.out -covermode=atomic ./...

go.sum

@@ -14,6 +14,8 @@ github.com/go-openapi/swag/jsonname v0.25.5 h1:8p150i44rv/Drip4vWI3kGi9+4W9TdI3U
 github.com/go-openapi/swag/jsonname v0.25.5/go.mod h1:jNqqikyiAK56uS7n8sLkdaNY/uq6+D2m2LANat09pKU=
 github.com/go-openapi/testify/v2 v2.4.0 h1:8nsPrHVCWkQ4p8h1EsRVymA2XABB4OT40gcvAu+voFM=
 github.com/go-openapi/testify/v2 v2.4.0/go.mod h1:HCPmvFFnheKK2BuwSA0TbbdxJ3I16pjwMkYkP4Ywn54=
+github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
+github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=

internal/e2e/dart_test.go

@@ -0,0 +1,178 @@
+package e2e
+
+import (
+	"fmt"
+	"maps"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/xseman/openapi-generator/internal/gen"
+)
+
+// dartVersion reads "Dart SDK version: 3.13.7 ..." as 3 and 13.
+var dartVersion = regexp.MustCompile(`version: (\d+)\.(\d+)`)
+
+// runDart generates a dart-fetch package per suite, depends on them from a
+// package holding testdata/e2e/runners/dart and runs the suites on the VM.
+// E2E_DART names the dart binary; the clients need Dart 3.13 or later.
+func runDart(t *testing.T, suites []suite) map[string]map[int]outcome {
+	t.Helper()
+
+	dart := os.Getenv("E2E_DART")
+	if dart == "" {
+		dart = "dart"
+	}
+
+	ver, err := exec.Command(dart, "--version").CombinedOutput()
+	if m := dartVersion.FindStringSubmatch(string(ver)); err != nil || m == nil || m[1] == "3" && atoi(m[2]) < 13 {
+		t.Skipf("dart-fetch clients need Dart 3.13 or later (set E2E_DART): %s %v", strings.TrimSpace(string(ver)), err)
+	}
+
+	dir := t.TempDir()
+
+	runner, err := os.ReadFile("../../testdata/e2e/runners/dart/runner.dart")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	write(t, filepath.Join(dir, "runner.dart"), string(runner))
+
+	for i, s := range suites {
+		err := gen.Generate(gen.Options{
+			InputSpec:            s.Spec,
+			OutputDir:            filepath.Join(dir, "c"+strconv.Itoa(i)),
+			GeneratorName:        "dart-fetch",
+			TemplateDir:          "../../templates/dart-fetch",
+			AdditionalProperties: []string{"pubName=c" + strconv.Itoa(i)},
+			SkipValidation:       true,
+		})
+		if err != nil {
+			t.Fatalf("generate %s: %v", s.Name, err)
+		}
+	}
+
+	// A client that does not compile would stop the whole program: it
+	// leaves the run, and its cases fail with its first error.
+	broken := dartErrors(t, dart, dir)
+	failed := map[string]map[int]outcome{}
+
+	var imports, clients, deps strings.Builder
+
+	for i, s := range suites {
+		pkg := "c" + strconv.Itoa(i)
+
+		if msg, ok := broken[pkg]; ok {
+			failed[s.Name] = map[int]outcome{}
+			for j := range s.Cases {
+				failed[s.Name][j] = outcome{Suite: s.Name, Case: j, Fail: "the client does not compile: " + msg}
+			}
+
+			continue
+		}
+
+		fmt.Fprintf(&deps, "  %s:\n    path: %s\n", pkg, pkg)
+		fmt.Fprintf(&imports, "import 'package:%s/%s.dart' as %s;\n", pkg, pkg, pkg)
+		fmt.Fprintf(&clients, "    %q: Client(\n      (base, a) => %s.Configuration(basePath: base, username: a.username, password: a.password, "+
+			"apiKey: (name) => a.apiKey ?? '', accessToken: () => a.bearer ?? ''),\n      (cfg) => [%s],\n      %q),\n",
+			s.Name, pkg, dartAPIs(t, filepath.Join(dir, pkg), pkg), pkg)
+	}
+
+	var running []suite
+
+	for _, s := range suites {
+		if _, ok := failed[s.Name]; !ok {
+			running = append(running, s)
+		}
+	}
+
+	if len(running) == 0 {
+		return failed
+	}
+
+	write(t, filepath.Join(dir, "pubspec.yaml"), "name: e2e_runner\npublish_to: none\nenvironment:\n  sdk: '>=3.13.0 <4.0.0'\ndependencies:\n"+deps.String())
+	write(t, filepath.Join(dir, "main.dart"), "import 'runner.dart';\n"+imports.String()+
+		"\nvoid main(List<String> args) => run(args[0], {\n"+clients.String()+"});\n")
+
+	get := exec.Command(dart, "pub", "get", "--offline")
+	get.Dir = dir
+
+	if out, err := get.CombinedOutput(); err != nil {
+		t.Fatalf("dart pub get: %v\n%s", err, out)
+	}
+
+	writeInput(t, dir, running)
+
+	cmd := exec.Command(dart, "run", "main.dart", filepath.Join(dir, "input.json"))
+	cmd.Dir = dir
+
+	out := execRunner(t, cmd)
+	maps.Copy(out, failed)
+
+	return out
+}
+
+// dartErrors analyzes the generated packages under dir and returns the
+// first compile error of each package that has one.
+func dartErrors(t *testing.T, dart, dir string) map[string]string {
+	t.Helper()
+
+	cmd := exec.Command(dart, "analyze", "--format=machine", ".")
+	cmd.Dir = dir
+
+	out, _ := cmd.CombinedOutput()
+
+	errs := map[string]string{}
+
+	for _, line := range strings.Split(string(out), "\n") {
+		f := strings.Split(line, "|")
+		if len(f) < 8 || f[0] != "ERROR" {
+			continue
+		}
+
+		rel, err := filepath.Rel(dir, f[3])
+		if err != nil {
+			continue
+		}
+
+		pkg, _, _ := strings.Cut(rel, string(filepath.Separator))
+		if _, seen := errs[pkg]; !seen {
+			errs[pkg] = fmt.Sprintf("%s:%s: %s", rel, f[4], f[7])
+		}
+	}
+
+	return errs
+}
+
+// dartAPIs lists the constructors of a package's API classes for cfg.
+func dartAPIs(t *testing.T, dir, pkg string) string {
+	t.Helper()
+
+	files, _ := filepath.Glob(filepath.Join(dir, "lib", "src", "apis", "*.dart"))
+	class := regexp.MustCompile(`(?m)^class (\w+) extends BaseApi`)
+
+	var calls []string
+
+	for _, f := range files {
+		data, err := os.ReadFile(f)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for _, m := range class.FindAllStringSubmatch(string(data), -1) {
+			calls = append(calls, pkg+"."+m[1]+"(cfg as "+pkg+".Configuration)")
+		}
+	}
+
+	return strings.Join(calls, ", ")
+}
+
+func atoi(s string) int {
+	n, _ := strconv.Atoi(s)
+
+	return n
+}