Do not filter on linux/amd64 per default (#805)

* Do not filter on linux/amd64 per default & add tests

Tasks with no platform would otherwise not perform on runners with different OS/ARCH combos

Signed-off-by: Lukas Bachschwell <lukas@lbsfilm.at>
Co-authored-by: 6543 <6543@obermui.de>

pipeline/frontend/metadata.go

@@ -218,8 +218,5 @@ func (m *Metadata) Environ() map[string]string {
 var pullRegexp = regexp.MustCompile(`\d+`)
 
 func (m *Metadata) SetPlatform(platform string) {
-	if platform == "" {
-		platform = "linux/amd64"
-	}
 	m.Sys.Arch = platform
 }

server/grpc/filter.go

@@ -39,6 +39,11 @@ func createFilterFunc(filter rpc.Filter) (queue.Filter, error) {
 		}
 
 		for k, v := range filter.Labels {
+			// if platform is not set ignore that filter
+			if k == "platform" && task.Labels[k] == "" {
+				continue
+			}
+
 			if task.Labels[k] != v {
 				return false
 			}

server/grpc/filter_test.go

@@ -0,0 +1,97 @@
+// Copyright 2022 Woodpecker Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package grpc
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/woodpecker-ci/woodpecker/pipeline/rpc"
+	"github.com/woodpecker-ci/woodpecker/server/queue"
+)
+
+func TestCreateFilterFunc(t *testing.T) {
+	t.Parallel()
+
+	type filterTests struct {
+		tsk queue.Task
+		exp bool
+	}
+
+	tests := []struct {
+		struc rpc.Filter
+		ft    []filterTests
+	}{{
+		struc: rpc.Filter{},
+		ft: []filterTests{{
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": "", "repo": "test/woodpecker"},
+			},
+			exp: true,
+		}, {
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": ""},
+			},
+			exp: true,
+		}},
+	}, {
+		struc: rpc.Filter{
+			Labels: map[string]string{"platform": "abc"},
+		},
+		ft: []filterTests{{
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": "def"},
+			},
+			exp: false,
+		}, {
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": ""},
+			},
+			exp: true,
+		}},
+	}, {
+		struc: rpc.Filter{
+			Expr: "platform = 'abc' OR repo = 'test/woodpecker'",
+		},
+		ft: []filterTests{{
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": "", "repo": "test/woodpecker"},
+			},
+			exp: true,
+		}, {
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": "abc", "repo": "else"},
+			},
+			exp: true,
+		}, {
+			tsk: queue.Task{
+				Labels: map[string]string{"platform": "also", "repo": "else"},
+			},
+			exp: false,
+		}},
+	}}
+
+	for _, test := range tests {
+		fn, err := createFilterFunc(test.struc)
+		if !assert.NoError(t, err) {
+			t.Fail()
+		}
+
+		for _, ft := range test.ft {
+			assert.EqualValues(t, ft.exp, fn(&ft.tsk))
+		}
+	}
+}