[milo] remove linkBase and calculate links directly.

milo/buildsource/swarming/build.go

Index: milo/buildsource/swarming/build.go
diff --git a/milo/buildsource/swarming/build.go b/milo/buildsource/swarming/build.go
index 50dc83772ef378332f5f8927bbf468d4cfddae54..118b25e5301004f2d3310a6a53db216f2028d742 100644
--- a/milo/buildsource/swarming/build.go
+++ b/milo/buildsource/swarming/build.go
@@ -14,6 +14,7 @@ import (
 
 	"golang.org/x/net/context"
 
+	"github.com/luci/gae/service/info"
 	swarming "github.com/luci/luci-go/common/api/swarming/swarming/v1"
 	"github.com/luci/luci-go/common/errors"
 	"github.com/luci/luci-go/common/logging"
@@ -546,7 +547,7 @@ func failedToStart(c context.Context, build *resp.MiloBuild, res *swarming.Swarm
 	return addTaskToBuild(c, host, res, build)
 }
 
-func (bl *BuildLoader) SwarmingBuildImpl(c context.Context, svc swarmingService, linkBase, taskID string) (*resp.MiloBuild, error) {
+func (bl *BuildLoader) SwarmingBuildImpl(c context.Context, svc swarmingService, taskID string) (*resp.MiloBuild, error) {
 	// Fetch the data from Swarming
 	var logDogStreamAddr *types.StreamAddr
 
@@ -657,11 +658,16 @@ func (bl *BuildLoader) SwarmingBuildImpl(c context.Context, svc swarmingService,
 		if lds != nil && lds.MainStream != nil && lds.MainStream.Data != nil {
 			s = lds.MainStream.Data
 		}
-		ub = swarmingURLBuilder(linkBase)
+
+		if ub, err = swarmingURLBuilderForTask(c, taskID); err != nil {
+			return nil, err
+		}
 
 	default:
 		s = &miloProto.Step{}
-		ub = swarmingURLBuilder(linkBase)
+		if ub, err = swarmingURLBuilderForTask(c, taskID); err != nil {
+			return nil, err
+		}
 	}
 
 	if s != nil {
@@ -730,10 +736,27 @@ func botPageURL(swarmingHostname, botID string) string {
 // swarmingURLBuilder is a logdog.URLBuilder that builds Milo swarming log
 // links.
 //
-// The string value for this should be the "linkBase" parameter value supplied
-// to swarmingBuildImpl.
+// Make one of these with swarmingURLBuilderForTask.
 type swarmingURLBuilder string
 
+// swarmingURLBuilderForTask returns a URLBuilder that builds links relative to
+// the current milo hostname's /swarming/task/<id> endpoint.
+func swarmingURLBuilderForTask(c context.Context, task string) (rawpresentation.URLBuilder, error) {

[Ryan Tseng, 2017/07/12 03:52:56]

Honestly relative urls are fine, most other places use relative URLs, this used
full URLs previously just because it was convenient.

[iannucci, 2017/07/12 18:08:36]

Done.

+	hostname, err := info.ModuleHostname(c, "", "", "")
+	if err != nil {
+		return nil, err
+	}
+	// version.module.hostname.tld
+	toks := strings.SplitN(hostname, ".", 3)
+	if len(toks) != 3 {
+		return nil, errors.Reason("unable to determine base URL").
+			InternalReason("bad ModuleHostname %q", hostname).Err()
+	}
+	return swarmingURLBuilder(fmt.Sprintf(
+		"https://%s-dot-%s-dot-%s/swarming/task/%s", toks[0], toks[1], toks[2], task,

[Ryan Tseng, 2017/07/12 03:52:56]

"/swarming/task/" + task 

is sufficient

Probably better too, since we don't really want to see blah-dot-blah in all the
places

[iannucci, 2017/07/12 18:08:36]

Done.

+	)), nil
+}
+
 func (b swarmingURLBuilder) BuildLink(l *miloProto.Link) *resp.Link {
 	u, err := url.Parse(string(b))
 	if err != nil {
@@ -744,11 +767,7 @@ func (b swarmingURLBuilder) BuildLink(l *miloProto.Link) *resp.Link {
 	case *miloProto.Link_LogdogStream:
 		ls := t.LogdogStream
 
-		if u.Path == "" {
-			u.Path = ls.Name
-		} else {
-			u.Path = strings.TrimSuffix(u.Path, "/") + "/" + ls.Name
-		}
+		u.Path += "/" + ls.Name
 		link := resp.NewLink(l.Label, u.String())
 		if link.Label == "" {
 			link.Label = ls.Name