jschoubben
0c8d0f73fa
delivery.NamedTree hashes the manifest digest with each named path's git object; catalogue.Manifest.NamedPaths gives the union of the paths, only when every artifact names some. The named: prefix keeps the value apart from a git tree id.
48 lines
2.2 KiB
Go
48 lines
2.2 KiB
Go
package delivery
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import (
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"crypto/sha256"
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"encoding/hex"
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"fmt"
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"path"
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"sort"
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"strings"
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)
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// NamedTreePrefix opens the tree input of a module whose every artifact names its paths, so such a value is never read
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// as a git tree id and a reader of a kept Tree can tell the two apart.
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const NamedTreePrefix = "named:"
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// NamedTree is the tree input of the new-form fingerprint of a module whose every artifact names the paths it is built
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// from (novox/hq ADR 0499 clause 2): `named:` and the hex sha256 of the lines "manifest <digest>" and, sorted,
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// "path <path> <object>", joined by a newline. manifest is the module's ManifestDigest (the sha256 of its module.json's
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// exact bytes, as Module.Manifest and the merge preview carry it); paths are the named paths, each clean and relative to
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// the module's directory as the manifest names them (catalogue.Manifest.NamedPaths), with the git object id each has at
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// the commit (a blob for a file, a tree for a directory).
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//
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// **One function computes it** (clause 2): the indexer, its merge preview (buildstep.ModuleTrees) and the build modules
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// call this one, and no second computation exists. It refuses no path, a named path with no object (absent at the
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// commit), a path that is not clean, and a manifest that is not a digest, naming them: the indexer then gives the
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// module none, with that reason (clause 3).
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func NamedTree(manifest string, paths map[string]string) (string, error) {
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if _, err := ManifestsKey(manifest); err != nil {
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return "", err
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}
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if len(paths) == 0 {
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return "", fmt.Errorf("delivery: the module names no path, so it has no named tree")
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}
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lines := make([]string, 0, len(paths))
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for p, object := range paths {
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if p == "" || p != path.Clean(p) || strings.HasPrefix(p, "/") || p == ".." || strings.HasPrefix(p, "../") {
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return "", fmt.Errorf("delivery: the named path %q is not a clean path inside the module's directory", p)
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}
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if object == "" {
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return "", fmt.Errorf("delivery: the named path %q has no git object at the commit", p)
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}
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lines = append(lines, "path "+p+" "+object)
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}
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sort.Strings(lines)
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sum := sha256.Sum256([]byte("manifest " + manifest + "\n" + strings.Join(lines, "\n")))
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return NamedTreePrefix + hex.EncodeToString(sum[:]), nil
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}
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