feat: Fail the go build early if go version is not compatible with go…

….mod file (#1292)

Fixes issue #1184

Note: `TestGenerateAllTypes` in `build_kotlin_test.go` is failing on
`main`. This PR touches the code for that but doesn't change any of the
behavior or assertions so it will continue to fail.

Tested manually as well:
```
$ ftl build highgoversion
info:highgoversion: Building module
ftl: error: go version "1.22.2" is not recent enough for this module, needs minimum version "9000.1.1"
```

buildengine/build_go_test.go

@@ -1,6 +1,8 @@
 package buildengine
 
 import (
+	"fmt"
+	"runtime"
 	"testing"
 
 	"github.com/TBD54566975/ftl/backend/schema"
@@ -120,7 +122,7 @@ func Nothing(context.Context) error {
 		buildDir:  "_ftl",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("go/modules/other/external_module.go", expected),
 	})
 }
@@ -169,7 +171,7 @@ func Call(context.Context, Req) (Resp, error) {
 		buildDir:  "_ftl",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("go/modules/test/external_module.go", expected),
 	})
 }
@@ -183,11 +185,37 @@ func TestExternalType(t *testing.T) {
 		buildDir:  "_ftl",
 		sch:       &schema.Schema{},
 	}
-	testBuild(t, bctx, true, []assertion{
+	testBuild(t, bctx, "unsupported external type", []assertion{
 		assertBuildProtoErrors(
 			"unsupported external type \"time.Month\"",
 			"unsupported type \"time.Month\" for field \"Month\"",
 			"unsupported response type \"ftl/external.ExternalResponse\"",
 		),
 	})
 }
+
+func TestGoModVersion(t *testing.T) {
+	if testing.Short() {
+		t.SkipNow()
+	}
+	sch := &schema.Schema{
+		Modules: []*schema.Module{
+			schema.Builtins(),
+			{Name: "highgoversion", Decls: []schema.Decl{
+				&schema.Data{Name: "EchoReq"},
+				&schema.Data{Name: "EchoResp"},
+				&schema.Verb{
+					Name:     "echo",
+					Request:  &schema.Ref{Name: "EchoRequest"},
+					Response: &schema.Ref{Name: "EchoResponse"},
+				},
+			}},
+		},
+	}
+	bctx := buildContext{
+		moduleDir: "testdata/projects/highgoversion",
+		buildDir:  "_ftl",
+		sch:       sch,
+	}
+	testBuild(t, bctx, fmt.Sprintf("go version %q is not recent enough for this module, needs minimum version \"9000.1.1\"", runtime.Version()[2:]), []assertion{})
+}

buildengine/build_kotlin_test.go

@@ -25,7 +25,7 @@ package ftl.test
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -152,7 +152,7 @@ data class TestResponse(
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -213,7 +213,7 @@ fun testVerb(context: Context, req: Request): ftl.builtin.Empty = throw
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -267,7 +267,7 @@ class Empty
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("generated-sources/ftl/builtin/Builtin.kt", expected),
 	})
 }
@@ -311,7 +311,7 @@ fun emptyVerb(context: Context, req: ftl.builtin.Empty): ftl.builtin.Empty = thr
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -391,7 +391,7 @@ fun nothing(context: Context): Unit = throw
 		buildDir:  "target",
 		sch:       sch,
 	}
-	testBuild(t, bctx, false, []assertion{
+	testBuild(t, bctx, "", []assertion{
 		assertGeneratedModule("generated-sources/ftl/test/Test.kt", expected),
 	})
 }
@@ -405,7 +405,8 @@ func TestKotlinExternalType(t *testing.T) {
 		buildDir:  "target",
 		sch:       &schema.Schema{},
 	}
-	testBuild(t, bctx, true, []assertion{
-		assertBuildProtoErrors("expected module name to be in the form ftl.<module>, but was com.google.type.DayOfWeek"),
+	expectedErrMsg := "expected module name to be in the form ftl.<module>, but was com.google.type.DayOfWeek"
+	testBuild(t, bctx, expectedErrMsg, []assertion{
+		assertBuildProtoErrors(expectedErrMsg),
 	})
 }

buildengine/build_test.go

@@ -23,7 +23,7 @@ type assertion func(t testing.TB, bctx buildContext) error
 func testBuild(
 	t *testing.T,
 	bctx buildContext,
-	expectFail bool,
+	expectedBuildErrMsg string, // emptystr if no error expected
 	assertions []assertion,
 ) {
 	t.Helper()
@@ -33,8 +33,9 @@ func testBuild(
 	module, err := LoadModule(abs)
 	assert.NoError(t, err)
 	err = Build(ctx, bctx.sch, module)
-	if expectFail {
+	if len(expectedBuildErrMsg) > 0 {
 		assert.Error(t, err)
+		assert.Contains(t, err.Error(), expectedBuildErrMsg)
 	} else {
 		assert.NoError(t, err)
 	}

buildengine/discover_test.go

@@ -102,6 +102,18 @@ func TestDiscoverModules(t *testing.T) {
 				},
 			},
 		},
+		Module{
+			ModuleConfig: moduleconfig.ModuleConfig{
+				Dir:       "testdata/projects/highgoversion",
+				Language:  "go",
+				Realm:     "home",
+				Module:    "highgoversion",
+				Deploy:    []string{"main"},
+				DeployDir: "_ftl",
+				Schema:    "schema.pb",
+				Watch:     []string{"**/*.go", "go.mod", "go.sum"},
+			},
+		},
 		Module{
 			ModuleConfig: moduleconfig.ModuleConfig{
 				Dir:       "testdata/projects/other",

buildengine/testdata/projects/highgoversion/ftl.toml

@@ -0,0 +1,2 @@
+module = "highgoversion"
+language = "go"

buildengine/testdata/projects/highgoversion/go.mod

@@ -0,0 +1,46 @@
+module ftl/highgoversion
+
+go 9000.1.1
+
+require github.com/TBD54566975/ftl v0.177.1
+
+require (
+	connectrpc.com/connect v1.16.0 // indirect
+	connectrpc.com/grpcreflect v1.2.0 // indirect
+	connectrpc.com/otelconnect v0.7.0 // indirect
+	github.com/BurntSushi/toml v1.3.2 // indirect
+	github.com/TBD54566975/scaffolder v0.8.0 // indirect
+	github.com/alecthomas/concurrency v0.0.2 // indirect
+	github.com/alecthomas/kong v0.9.0 // indirect
+	github.com/alecthomas/participle/v2 v2.1.1 // indirect
+	github.com/alecthomas/types v0.14.0 // indirect
+	github.com/alessio/shellescape v1.4.2 // indirect
+	github.com/danieljoos/wincred v1.2.0 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/godbus/dbus/v5 v5.1.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
+	github.com/jackc/pgx/v5 v5.5.5 // indirect
+	github.com/jackc/puddle/v2 v2.2.1 // indirect
+	github.com/jpillora/backoff v1.0.0 // indirect
+	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/multiformats/go-base36 v0.2.0 // indirect
+	github.com/swaggest/jsonschema-go v0.3.70 // indirect
+	github.com/swaggest/refl v1.3.0 // indirect
+	github.com/zalando/go-keyring v0.2.4 // indirect
+	go.opentelemetry.io/otel v1.25.0 // indirect
+	go.opentelemetry.io/otel/metric v1.25.0 // indirect
+	go.opentelemetry.io/otel/trace v1.25.0 // indirect
+	golang.org/x/crypto v0.22.0 // indirect
+	golang.org/x/exp v0.0.0-20240222234643-814bf88cf225 // indirect
+	golang.org/x/mod v0.17.0 // indirect
+	golang.org/x/net v0.24.0 // indirect
+	golang.org/x/sync v0.7.0 // indirect
+	golang.org/x/sys v0.19.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	google.golang.org/protobuf v1.33.0 // indirect
+)
+
+replace github.com/TBD54566975/ftl => /Users/dli/Development/ftl

buildengine/testdata/projects/highgoversion/highgoversion.go

@@ -0,0 +1,21 @@
+package highgoversion
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/TBD54566975/ftl/go-runtime/ftl" // Import the FTL SDK.
+)
+
+type EchoRequest struct {
+	Name ftl.Option[string] `json:"name"`
+}
+
+type EchoResponse struct {
+	Message string `json:"message"`
+}
+
+//ftl:export
+func Echo(ctx context.Context, req EchoRequest) (EchoResponse, error) {
+	return EchoResponse{Message: fmt.Sprintf("Hello, %s!", req.Name.Default("anonymous"))}, nil
+}