vpython/spec/spec.go

// Copyright 2017 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package spec

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"sort"

	"go.chromium.org/luci/vpython/api/vpython"

	"go.chromium.org/luci/common/data/sortby"
	"go.chromium.org/luci/common/errors"

	"github.com/golang/protobuf/proto"
)

// Render creates a human-readable string from spec.
func Render(spec *vpython.Spec) string { return proto.MarshalTextString(spec) }

// NormalizeSpec normalizes the specification Message such that two messages
// with identical meaning will have identical representation.
//
// If multiple wheel entries exist for the same package name, they must also
// share a version. If they don't, an error will be returned. Otherwise, they
// will be merged into a single wheel entry.
//
// NormalizeSpec will prune any Wheel entries that don't match the specified
// tags, and will remove the match entries from any remaining Wheel entries.
func NormalizeSpec(spec *vpython.Spec, tags []*vpython.PEP425Tag) error {
	// If we have a VirtualEnv package, validate and normalize it.
	if pkg := spec.Virtualenv; pkg != nil {
		if len(pkg.MatchTag) > 0 {
			// The VirtualEnv package may not specify a match tag.
			pkg.MatchTag = nil
		}
	}

	// Apply match filters, prune any entries that don't match, and clear the
	// MatchTag entries for those that do.
	//
	// Make sure the VirtualEnv package isn't listed in the wheels list.
	//
	// Track the versions for each package and assert that any duplicate packages
	// don't share a version.
	pos := 0
	packageVersions := make(map[string]string, len(spec.Wheel))
	for _, w := range spec.Wheel {
		if spec.Virtualenv != nil && spec.Virtualenv.Name == w.Name {
			return errors.Reason("wheel %q cannot be the VirtualEnv package", w.Name).Err()
		}

		// If this package doesn't match the tag set, skip it.
		if !PackageMatches(w, tags) {
			continue
		}

		// If this package has already been included, assert version consistency.
		if v, ok := packageVersions[w.Name]; ok {
			if v != w.Version {
				return errors.Reason("multiple versions for package %q: %q != %q", w.Name, w.Version, v).Err()
			}

			// This package has already been included, so we can ignore it.
			continue
		}

		// Mark that this package was included, so we can assert version consistency
		// and avoid duplicates.
		packageVersions[w.Name] = w.Version
		w.MatchTag = nil
		spec.Wheel[pos] = w
		pos++
	}
	spec.Wheel = spec.Wheel[:pos]
	sort.Sort(specPackageSlice(spec.Wheel))
	return nil
}

// Hash hashes the contents of the supplied "spec" and "rt" and returns the
// result as a hex-encoded string.
//
// If not empty, the contents of extra are prefixed to hash string. This can
// be used to factor additional influences into the spec hash.
func Hash(spec *vpython.Spec, rt *vpython.Runtime, extra ...string) string {
	mustMarshal := func(msg proto.Message) []byte {
		data, err := proto.Marshal(msg)
		if err != nil {
			panic(fmt.Errorf("failed to marshal proto: %v", err))
		}
		return data
	}
	specData := mustMarshal(spec)
	rtData := mustMarshal(rt)

	mustWrite := func(v int, err error) {
		if err != nil {
			panic(fmt.Errorf("impossible: %s", err))
		}
	}

	hash := sha256.New()
	for _, s := range extra {
		mustWrite(fmt.Fprintf(hash, "%s:", s))
	}
	mustWrite(fmt.Fprintf(hash, "%s:", vpython.Version))
	mustWrite(hash.Write(specData))
	mustWrite(hash.Write([]byte(":")))
	mustWrite(hash.Write(rtData))
	return hex.EncodeToString(hash.Sum(nil))
}

type specPackageSlice []*vpython.Spec_Package

func (s specPackageSlice) Len() int      { return len(s) }
func (s specPackageSlice) Swap(i, j int) { s[i], s[j] = s[j], s[i] }

func (s specPackageSlice) Less(i, j int) bool {
	return sortby.Chain{
		func(i, j int) bool { return s[i].Name < s[j].Name },
		func(i, j int) bool { return s[i].Version < s[j].Version },
	}.Use(i, j)
}

type pep425TagSlice []*vpython.PEP425Tag

func (s pep425TagSlice) Len() int      { return len(s) }
func (s pep425TagSlice) Swap(i, j int) { s[i], s[j] = s[j], s[i] }

func (s pep425TagSlice) Less(i, j int) bool {
	return sortby.Chain{
		func(i, j int) bool { return s[i].Python < s[j].Python },
		func(i, j int) bool { return s[i].Abi < s[j].Abi },
		func(i, j int) bool { return s[i].Platform < s[j].Platform },
	}.Use(i, j)
}