Add structured coroutines and explicit error handling

internal/lang/result_test.go

@@ -0,0 +1,142 @@
+package lang
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestResultQuestionPropagatesGoError(t *testing.T) {
+	prog, err := Parse(`package demo
+import strconv
+fun parse(value: String): Result<Int, Error> {
+    val parsed = strconv.atoi(value)?
+    return Result::Ok(parsed)
+}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{"parsed, gotlinError1 := strconv.Atoi(value)", "if gotlinError1 != nil {", "GotlinResult[int]{Err: gotlinError1}", "GotlinResult[int]{Value: parsed}"} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestGoValueAndErrorReturnConvertsToResult(t *testing.T) {
+	prog, err := Parse(`package demo
+import strconv
+fun parse(value: String): Result<Int, Error> { return strconv.atoi(value) }
+fun assign(value: String) { val result: Result<Int, Error> = strconv.atoi(value); println(result.unwrapOr(0)) }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{
+		"value, err := strconv.Atoi(value)",
+		"GotlinResult[int]{Value: value, Err: err}",
+		"var result GotlinResult[int] = func() GotlinResult[int]",
+	} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestGoErrorOnlyReturnConvertsToUnitResult(t *testing.T) {
+	prog, err := Parse(`package demo
+import os
+fun changeDirectory(path: String): Result<Unit, Error> { return os.chdir(path) }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{
+		"func changeDirectory(path string) GotlinResult[struct{}]",
+		"err := os.Chdir(path)",
+		"GotlinResult[struct{}]{Err: err}",
+	} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestResultQuestionPropagatesGotlinResult(t *testing.T) {
+	prog, err := Parse(`package demo
+import errors
+fun inner(ok: Boolean): Result<String, Error> { if (!ok) { return Result::Err(errors.new("failed")) }; return Result::Ok("ok") }
+fun outer(): Result<String, Error> { val value = inner(true)?; return Result::Ok(value) }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{"gotlinResult1 := inner(true)", "gotlinResult1.Err", "value := gotlinResult1.Value"} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestResultUnwrapAndUnwrapOr(t *testing.T) {
+	prog, err := Parse(`package demo
+fun value(result: Result<String, Error>): String { return result.unwrapOr("fallback") }
+fun required(result: Result<String, Error>): String { return result.unwrap() }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, want := range []string{"gotlinResultUnwrapOr(result, \"fallback\")", "gotlinResultUnwrap(result)"} {
+		if !strings.Contains(string(out), want) {
+			t.Fatalf("missing %q:\n%s", want, out)
+		}
+	}
+}
+
+func TestQuestionRequiresResultFunction(t *testing.T) {
+	prog, err := Parse(`package demo
+import strconv
+fun parse(value: String): Int { val parsed = strconv.atoi(value)?; return parsed }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = GenerateGo(prog)
+	if err == nil || !strings.Contains(err.Error(), "returning Result") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestQuestionUseKeepsReferencedVariableLive(t *testing.T) {
+	prog, err := Parse(`package demo
+import strconv
+fun parse(value: String): Result<Int, Error> {
+    val input = value
+    val parsed = strconv.atoi(input)?
+    return Result::Ok(parsed)
+}`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := GenerateGo(prog)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(out), "input := value") || strings.Contains(string(out), "_ = value") {
+		t.Fatalf("variable used by ? expression was removed:\n%s", out)
+	}
+}