Enable clear/purge for failed digests

golden/go/diff/diff.go

 package diff
 
 import (
         "image"
         "image/color"
         "image/draw"
         "image/png"
         "math"
         "os"
         "unsafe"
@@ skipping 70 matching lines @@
 )
 
 // DigestFailure captures the details of a digest error that occured.
 type DigestFailure struct {
         Digest string  `json:"digest"`
         Reason DiffErr `json:"reason"`
         TS     int64   `json:"ts"`
         Error  string  `json:"error"`
 }
 
+// Implement sort.Interface for a slice of DigestFailure
+type DigestFailureSlice []*DigestFailure
+
+func (d DigestFailureSlice) Len() int           { return len(d) }
+func (d DigestFailureSlice) Less(i, j int) bool { return d[i].TS < d[j].TS }
+func (d DigestFailureSlice) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
+
 type DiffStore interface {
         // Get returns the DiffMetrics of the provided dMain digest vs all digests
         // specified in dRest.
         Get(dMain string, dRest []string) (map[string]*DiffMetrics, error)
 
         // AbsPath returns the paths of the images that correspond to the given
         // image digests.
         AbsPath(digest []string) map[string]string
 
         // UnavailableDigests returns map[digest]*DigestFailure which can be used
         // to check whether a digest could not be processed and to provide details
         // about failures.
         UnavailableDigests() map[string]*DigestFailure
 
         // PurgeDigests removes all information related to the indicated digests
         // (image, diffmetric) from local caches. If purgeGS is true it will also
         // purge the digests image from Google storage, forcing that the digest
         // be re-uploaded by the build bots.
-        PurgeDigests(digests []string, purgeGS bool)
+        PurgeDigests(digests []string, purgeGS bool) error
 
         // SetDigestSets sets the sets of digests we want to compare grouped by
         // names (usually test names). This sets the digests we are currently
         // interested in and removes digests (and their diffs) that we are no
         // longer interested in.
         SetDigestSets(namedDigestSets map[string]map[string]bool)
 }
 
 // OpenImage is a utility function that opens the specified file and returns an
 // image.Image
@@ skipping 178 matching lines @@
                         }
                 }
         }
 
         return &DiffMetrics{
                 NumDiffPixels:    numDiffPixels,
                 PixelDiffPercent: getPixelDiffPercent(numDiffPixels, totalPixels),
                 MaxRGBADiffs:     maxRGBADiffs,
                 DimDiffer:        (cmpWidth != resultWidth) || (cmpHeight != resultHeight)}, resultImg
 }