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https://github.com/dolthub/dolt.git
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e2f261b142
We now compute the commit type based on the type of the value and
the type of the parents.
For the first commit we get:
```
struct Commit {
parents: Set<Ref<Cycle<0>>>,
value: T,
}
```
As long as we continue to commit values with type T that type stays
the same.
When we later commits a value of type U we get:
```
struct Commit {
parents: Set<Ref<struct Commit {
parents: Set<Ref<Cycle<0>>>,
value: T | U
}>>,
value: U,
}
```
The new type gets combined as a union type for the value of the inner
commit struct.
Fixes #1495
115 lines
3.1 KiB
Go
115 lines
3.1 KiB
Go
// Copyright 2016 Attic Labs, Inc. All rights reserved.
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// Licensed under the Apache License, version 2.0:
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// http://www.apache.org/licenses/LICENSE-2.0
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package datas
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import (
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"github.com/attic-labs/noms/go/d"
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"github.com/attic-labs/noms/go/types"
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)
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const (
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ParentsField = "parents"
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ValueField = "value"
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)
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var valueCommitType = makeCommitType(types.ValueType)
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// NewCommit creates a new commit object. The type of Commit is computed based on the type of the value and the type of the parents.
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//
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// For the first commit we get:
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//
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// ```
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// struct Commit {
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// parents: Set<Ref<Cycle<0>>>,
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// value: T,
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// }
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// ```
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//
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// As long as we continue to commit values with type T that type stays the same.
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//
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// When we later commits a value of type U we get:
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//
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// ```
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// struct Commit {
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// parents: Set<Ref<struct Commit {
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// parents: Set<Ref<Cycle<0>>>,
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// value: T | U
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// }>>,
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// value: U,
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// }
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// ```
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//
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// The new type gets combined as a union type for the value of the inner commit struct.
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func NewCommit(value types.Value, parents types.Set) types.Struct {
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t := makeCommitType(value.Type(), valueTypesFromParents(parents)...)
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return types.NewStructWithType(t, types.ValueSlice{parents, value})
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}
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func makeCommitType(valueType *types.Type, parentsValueTypes ...*types.Type) *types.Type {
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tmp := make([]*types.Type, len(parentsValueTypes)+1)
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copy(tmp, parentsValueTypes)
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tmp[len(tmp)-1] = valueType
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parentsValueUnionType := types.MakeUnionType(tmp...)
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if parentsValueUnionType.Equals(valueType) {
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return types.MakeStructType("Commit", []string{
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ParentsField, ValueField,
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}, []*types.Type{
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types.MakeSetType(types.MakeRefType(types.MakeCycleType(0))),
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valueType,
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})
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}
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return types.MakeStructType("Commit", []string{ParentsField, ValueField}, []*types.Type{
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types.MakeSetType(types.MakeRefType(types.MakeStructType("Commit", []string{
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ParentsField, ValueField,
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}, []*types.Type{
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types.MakeSetType(types.MakeRefType(types.MakeCycleType(0))),
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parentsValueUnionType,
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}))),
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valueType,
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})
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}
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func valueTypesFromParents(parents types.Set) []*types.Type {
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elemType := getSetElementType(parents.Type())
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switch elemType.Kind() {
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case types.UnionKind:
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ts := []*types.Type{}
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for _, rt := range elemType.Desc.(types.CompoundDesc).ElemTypes {
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ts = append(ts, valueFromRefOfCommit(rt))
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}
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return ts
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default:
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return []*types.Type{valueFromRefOfCommit(elemType)}
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}
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}
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func getSetElementType(t *types.Type) *types.Type {
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d.Chk.True(t.Kind() == types.SetKind)
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return t.Desc.(types.CompoundDesc).ElemTypes[0]
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}
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func valueFromRefOfCommit(t *types.Type) *types.Type {
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return valueTypeFromCommit(getRefElementType(t))
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}
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func getRefElementType(t *types.Type) *types.Type {
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d.Chk.True(t.Kind() == types.RefKind)
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return t.Desc.(types.CompoundDesc).ElemTypes[0]
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}
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func valueTypeFromCommit(t *types.Type) *types.Type {
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d.Chk.True(t.Kind() == types.StructKind && t.Name() == "Commit")
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return t.Desc.(types.StructDesc).Field(ValueField)
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}
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func IsCommitType(t *types.Type) bool {
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return types.IsSubtype(valueCommitType, t)
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}
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func isRefOfCommitType(t *types.Type) bool {
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return t.Kind() == types.RefKind && IsCommitType(getRefElementType(t))
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}
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