preflight: Add filter API

Currently, generating the list of preflight checks used by
CleanUpHost/SetupHost and StartPreflightChecks is quite convoluted. We
have multiple Check[] arrays, which are picked or not depending on
various parameters (distro, network mode, experimental, ...).

When adding a new check, one needs to take all of this into account
before their check is used at the expected time.

This patch introduces a new API which uses the labels added to  each
individual Check definition.
getAllPreflightChecks/getPreflightChecks will then be modified to make
use of it, and automatically select the tests which should be used
depending on the labels which are set.

pkg/crc/preflight/labels.go

@@ -1,5 +1,11 @@
 package preflight
 
+import (
+	"runtime"
+
+	"github.com/code-ready/crc/pkg/crc/network"
+)
+
 type LabelName uint32
 
 const (
@@ -31,3 +37,57 @@ var (
 )
 
 type labels map[LabelName]LabelValue
+
+type preflightFilter map[LabelName]LabelValue
+
+func newFilter() preflightFilter {
+	switch runtime.GOOS {
+	case "darwin":
+		return preflightFilter{Os: Darwin}
+	case "linux":
+		return preflightFilter{Os: Linux}
+	case "windows":
+		return preflightFilter{Os: Windows}
+	}
+	// Should not happen
+	return preflightFilter{Os: Linux}
+}
+
+func (filter preflightFilter) SetNetworkMode(networkMode network.Mode) {
+	switch networkMode {
+	case network.SystemNetworkingMode:
+		filter[NetworkMode] = System
+	case network.UserNetworkingMode:
+		filter[NetworkMode] = User
+	}
+}
+
+/* This will iterate over 'checks' and only keep the checks which match the filter:
+ * - if a key is present in the filter and not in the check labels, the check is kept
+ * - if a key is present in the check labels, but not in the filter, the check is kept
+ * - if a key is present both in the filter and in the check labels, the check
+ *   is kept only if they have the same value, it is dropped if their values differ
+ */
+func (filter preflightFilter) Apply(checks []Check) []Check {
+	var filteredChecks []Check
+
+	for _, check := range checks {
+		if !skipCheck(check, filter) {
+			filteredChecks = append(filteredChecks, check)
+		}
+
+	}
+
+	return filteredChecks
+}
+
+func skipCheck(check Check, filter preflightFilter) bool {
+	for filterKey, filterValue := range filter {
+		checkValue, present := check.labels[filterKey]
+		if present && checkValue != filterValue {
+			return true
+		}
+	}
+
+	return false
+}

pkg/crc/preflight/preflight_darwin.go

@@ -110,6 +110,14 @@ const (
 	Disabled
 )
 
+func (filter preflightFilter) SetTray(enable bool) {
+	if version.IsMacosInstallPathSet() && enable {
+		filter[Tray] = Enabled
+	} else {
+		filter[Tray] = Disabled
+	}
+}
+
 // We want all preflight checks including
 // - experimental checks
 // - tray checks when using an installer, regardless of tray enabled or not

pkg/crc/preflight/preflight_linux.go

@@ -266,6 +266,22 @@ const (
 	SystemdResolved
 )
 
+func (filter preflightFilter) SetSystemdResolved(usingSystemdResolved bool) {
+	if usingSystemdResolved {
+		filter[DNS] = SystemdResolved
+	} else {
+		filter[DNS] = Dnsmasq
+	}
+}
+
+func (filter preflightFilter) SetDistro(distro *linux.OsRelease) {
+	if distroIsLike(distro, linux.Ubuntu) {
+		filter[Distro] = UbuntuLike
+	} else {
+		filter[Distro] = Other
+	}
+}
+
 // We want all preflight checks
 // - matching the current distro
 // - matching the networking daemon in use (NetworkManager or systemd-resolved) regardless of user/system networking

pkg/crc/preflight/preflight_windows.go

@@ -174,6 +174,14 @@ const (
 	Disabled
 )
 
+func (filter preflightFilter) SetTray(enable bool) {
+	if version.IsMsiBuild() && enable {
+		filter[Tray] = Enabled
+	} else {
+		filter[Tray] = Disabled
+	}
+}
+
 // We want all preflight checks including
 // - experimental checks
 // - tray checks when using an installer, regardless of tray enabled or not