Add func to print string inputs to hashing

Fixes sdboyer/gps#137

hash.go

@@ -16,14 +16,21 @@ import (
 // unnecessary.
 //
 // (Basically, this is for memoization.)
-func (s *solver) HashInputs() []byte {
+func (s *solver) HashInputs() (digest []byte) {
+	buf := new(bytes.Buffer)
+	s.writeHashingInputs(buf)
+
+	hd := sha256.Sum256(buf.Bytes())
+	digest = hd[:]
+	return
+}
+
+func (s *solver) writeHashingInputs(buf *bytes.Buffer) {
 	// Apply overrides to the constraints from the root. Otherwise, the hash
 	// would be computed on the basis of a constraint from root that doesn't
 	// actually affect solving.
 	p := s.ovr.overrideAll(s.rm.DependencyConstraints().merge(s.rm.TestDependencyConstraints()))
 
-	// Build up a buffer of all the inputs.
-	buf := new(bytes.Buffer)
 	for _, pd := range p {
 		buf.WriteString(string(pd.Ident.ProjectRoot))
 		buf.WriteString(pd.Ident.Source)
@@ -103,9 +110,18 @@ func (s *solver) HashInputs() []byte {
 	an, av := s.b.AnalyzerInfo()
 	buf.WriteString(an)
 	buf.WriteString(av.String())
+}
 
-	hd := sha256.Sum256(buf.Bytes())
-	return hd[:]
+// HashingInputsAsString returns the raw input data used by Solver.HashInputs()
+// as a string.
+//
+// This is primarily intended for debugging purposes.
+func HashingInputsAsString(s Solver) string {
+	ts := s.(*solver)
+	buf := new(bytes.Buffer)
+	ts.writeHashingInputs(buf)
+
+	return buf.String()
 }
 
 type sortPackageOrErr []PackageOrErr

hash_test.go

@@ -3,6 +3,7 @@ package gps
 import (
 	"bytes"
 	"crypto/sha256"
+	"strings"
 	"testing"
 )
 
@@ -42,7 +43,12 @@ func TestHashInputs(t *testing.T) {
 	correct := h.Sum(nil)
 
 	if !bytes.Equal(dig, correct) {
-		t.Errorf("Hashes are not equal")
+		t.Error("Hashes are not equal")
+	}
+
+	fixstr, hisstr := strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
 	}
 }
 
@@ -94,6 +100,11 @@ func TestHashInputsReqsIgs(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr := strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// Add requires
 	rm.req = map[string]bool{
 		"baz": true,
@@ -137,6 +148,11 @@ func TestHashInputsReqsIgs(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// remove ignores, just test requires alone
 	rm.ig = nil
 	params.Manifest = rm
@@ -173,6 +189,11 @@ func TestHashInputsReqsIgs(t *testing.T) {
 	if !bytes.Equal(dig, correct) {
 		t.Errorf("Hashes are not equal")
 	}
+
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
 }
 
 func TestHashInputsOverrides(t *testing.T) {
@@ -224,6 +245,11 @@ func TestHashInputsOverrides(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr := strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// Override not in root, just with constraint
 	rm.ovr["d"] = ProjectProperties{
 		Constraint: NewBranch("foobranch"),
@@ -257,6 +283,11 @@ func TestHashInputsOverrides(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// Override not in root, both constraint and network name
 	rm.ovr["e"] = ProjectProperties{
 		Source:     "groucho",
@@ -294,6 +325,11 @@ func TestHashInputsOverrides(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// Override in root, just constraint
 	rm.ovr["a"] = ProjectProperties{
 		Constraint: NewVersion("fluglehorn"),
@@ -332,6 +368,11 @@ func TestHashInputsOverrides(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// Override in root, only network name
 	rm.ovr["a"] = ProjectProperties{
 		Source: "nota",
@@ -371,6 +412,11 @@ func TestHashInputsOverrides(t *testing.T) {
 		t.Errorf("Hashes are not equal")
 	}
 
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
+
 	// Override in root, network name and constraint
 	rm.ovr["a"] = ProjectProperties{
 		Source:     "nota",
@@ -411,4 +457,9 @@ func TestHashInputsOverrides(t *testing.T) {
 	if !bytes.Equal(dig, correct) {
 		t.Errorf("Hashes are not equal")
 	}
+
+	fixstr, hisstr = strings.Join(elems, ""), HashingInputsAsString(s)
+	if fixstr != hisstr {
+		t.Errorf("Hashing inputs not equal:\n\t(GOT) %s\n\t(WNT) %s", hisstr, fixstr)
+	}
 }

solver.go

@@ -173,10 +173,10 @@ type solver struct {
 // a "lock file" - and/or use it to write out a directory tree of dependencies,
 // suitable to be a vendor directory, via CreateVendorTree.
 type Solver interface {
-	// HashInputs produces a hash digest representing the unique inputs to this
-	// solver. It is guaranteed that, if the hash digest is equal to the digest
-	// from a previous Solution.InputHash(), that that Solution is valid for
-	// this Solver's inputs.
+	// HashInputs hashes the unique inputs to this solver, returning the hash
+	// digest. It is guaranteed that, if the resulting digest is equal to the
+	// digest returned from a previous Solution.InputHash(), that that Solution
+	// is valid for this Solver's inputs.
 	//
 	// In such a case, it may not be necessary to run Solve() at all.
 	HashInputs() []byte