Improve error graph for failed solve

We were missing a couple of edges that would help make it clearer why
we were solving a constraint.

In particular, this DepError was problematic:

https://github.com/chainguard-dev/apko/blob/995ee5a40608591b2c4d2e7893abdffeca93f6ff/pkg/apk/apk/repo.go#L798

We were returning an error for the outer "pkg" and not including the
context of the constraint within that package being solved or the
failure of the selected package to solve its deps.

Signed-off-by: Jon Johnson <[email protected]>

pkg/apk/apk/repo.go

@@ -540,13 +540,13 @@ func (p *PkgResolver) GetPackageWithDependencies(pkgName string, existing map[st
 
 	pkg, err := p.resolvePackage(pkgName, dq)
 	if err != nil {
-		return nil, nil, nil, err
+		return nil, nil, nil, &ConstraintError{pkgName, err}
 	}
 
 	pin := cachedResolvePackageNameVersionPin(pkgName).pin
 	deps, conflicts, err := p.getPackageDependencies(pkg, pin, true, parents, localExisting, existingOrigins, dq)
 	if err != nil {
-		return nil, nil, nil, err
+		return nil, nil, nil, &DepError{pkg, err}
 	}
 	// eliminate duplication in dependencies
 	added := make(map[string]*RepositoryPackage, len(deps))
@@ -605,14 +605,14 @@ func (p *PkgResolver) ResolvePackage(pkgName string, dq map[*RepositoryPackage]s
 	name, version, compare, pin := constraint.name, constraint.version, constraint.dep, constraint.pin
 	pkgsWithVersions, ok := p.nameMap[name]
 	if !ok {
-		return nil, fmt.Errorf("could not find package that provides %s in indexes", pkgName)
+		return nil, fmt.Errorf("nothing provides %q", name)
 	}
 
 	// pkgsWithVersions contains a map of all versions of the package
 	// get the one that most matches what was requested
 	packages := filterPackages(pkgsWithVersions, dq, withVersion(version, compare), withPreferPin(pin))
 	if len(packages) == 0 {
-		return nil, maybedqerror(pkgName, pkgsWithVersions, dq)
+		return nil, maybedqerror(pkgsWithVersions, dq)
 	}
 	p.sortPackages(packages, nil, name, nil, nil, pin)
 	pkgs := make([]*RepositoryPackage, 0, len(packages))
@@ -632,14 +632,14 @@ func (p *PkgResolver) resolvePackage(pkgName string, dq map[*RepositoryPackage]s
 
 	pkgsWithVersions, ok := p.nameMap[name]
 	if !ok {
-		return nil, fmt.Errorf("could not find package, alias or a package that provides %s in indexes", pkgName)
+		return nil, fmt.Errorf("nothing provides %q", name)
 	}
 
 	// pkgsWithVersions contains a map of all versions of the package
 	// get the one that most matches what was requested
 	packages := filterPackages(pkgsWithVersions, dq, withVersion(version, compare), withPreferPin(pin))
 	if len(packages) == 0 {
-		return nil, maybedqerror(pkgName, pkgsWithVersions, dq)
+		return nil, maybedqerror(pkgsWithVersions, dq)
 	}
 	return p.bestPackage(packages, nil, name, nil, nil, pin).RepositoryPackage, nil
 }
@@ -688,7 +688,7 @@ func (p *PkgResolver) getPackageDependencies(pkg *RepositoryPackage, allowPin st
 	constraints := slices.Clone(pkg.Dependencies)
 
 	if err := p.constrain(constraints, dq); err != nil {
-		return nil, nil, fmt.Errorf("constraining deps for %q: %w", pkg.Filename(), err)
+		return nil, nil, fmt.Errorf("constraining deps: %w", err)
 	}
 
 	for len(constraints) != 0 {
@@ -736,7 +736,7 @@ func (p *PkgResolver) getPackageDependencies(pkg *RepositoryPackage, allowPin st
 			// first see if it is a name of a package
 			depPkgWithVersions, ok := p.nameMap[name]
 			if !ok {
-				return nil, nil, fmt.Errorf("could not find package either named %s or that provides %s for %s", dep, dep, pkg.Name)
+				return nil, nil, &ConstraintError{dep, fmt.Errorf("nothing provides %q", name)}
 			}
 			// pkgsWithVersions contains a map of all versions of the package
 			// get the one that most matches what was requested
@@ -747,7 +747,7 @@ func (p *PkgResolver) getPackageDependencies(pkg *RepositoryPackage, allowPin st
 				withInstalledPackage(existing[name]),
 			)
 			if len(pkgs) == 0 {
-				return nil, nil, &DepError{pkg, maybedqerror(dep, depPkgWithVersions, dq)}
+				return nil, nil, &ConstraintError{dep, maybedqerror(depPkgWithVersions, dq)}
 			}
 			options[dep] = pkgs
 		}
@@ -779,7 +779,7 @@ func (p *PkgResolver) getPackageDependencies(pkg *RepositoryPackage, allowPin st
 
 		best := p.bestPackage(pkgs, nil, name, existing, existingOrigins, "")
 		if best == nil {
-			return nil, nil, fmt.Errorf("could not find package for %q", name)
+			return nil, nil, &ConstraintError{name, fmt.Errorf("could not find package for %q", name)}
 		}
 
 		depPkg := best.RepositoryPackage
@@ -795,7 +795,7 @@ func (p *PkgResolver) getPackageDependencies(pkg *RepositoryPackage, allowPin st
 		childParents[pkg.Name] = true
 		subDeps, confs, err := p.getPackageDependencies(depPkg, allowPin, true, childParents, existing, existingOrigins, dq)
 		if err != nil {
-			return nil, nil, &DepError{pkg, err}
+			return nil, nil, &ConstraintError{name, &DepError{depPkg, err}}
 		}
 		// first add the children, then the parent (depth-first)
 		dependencies = append(dependencies, subDeps...)
@@ -1025,7 +1025,7 @@ func (e *DisqualifiedError) Unwrap() error {
 	return e.Wrapped
 }
 
-func maybedqerror(constraint string, pkgs []*repositoryPackage, dq map[*RepositoryPackage]string) error {
+func maybedqerror(pkgs []*repositoryPackage, dq map[*RepositoryPackage]string) error {
 	errs := make([]error, 0, len(pkgs))
 	for _, pkg := range pkgs {
 		reason, ok := dq[pkg.RepositoryPackage]
@@ -1035,10 +1035,10 @@ func maybedqerror(constraint string, pkgs []*repositoryPackage, dq map[*Reposito
 	}
 
 	if len(errs) != 0 {
-		return &ConstraintError{constraint, errors.Join(errs...)}
+		return errors.Join(errs...)
 	}
 
-	return fmt.Errorf("could not find constraint %q in indexes", constraint)
+	return errors.New("not in indexes")
 }
 
 func disqualifyDifference(ctx context.Context, byArch map[string][]NamedIndex) map[*RepositoryPackage]string {