mirror of https://github.com/hashicorp/consul
80 lines
5.5 KiB
Go
80 lines
5.5 KiB
Go
// Copyright (c) HashiCorp, Inc.
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// SPDX-License-Identifier: BUSL-1.1
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// The protohcl package aims to define a canonical way to translate between
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// protobuf and HCL encodings of data.
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//
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// Similar to google.golang.org/protobuf/encoding/protojson it intends to be
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// opinionated about what the canonical HCL representation of a protobuf type
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// should be.
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//
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// As HCL is a user centric data format as opposed to JSON/Protobuf which
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// are intended to be used more by machines, efficiency is not a primary goal
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// of this package as it is expected that users are either doing the encoding to and
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// decoding from HCL at the edge (such as within the Consul CLI) or that even
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// when done on servers, the rate that servers perform these translations should
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// be low enough to have any inefficiency produce a tangible performance impact.
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//
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// HCL has two different syntaxes that could be used to represent data: attribute and block
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//
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// This implementation chooses to represent primitive values, enums and the well known wrapper types and
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// collections of these values (maps and repeated fields) with attribute syntax. Other messages and collections
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// with message value types will be represented with block syntax for example
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//
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// message Foo {
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// map<string, int32> map_of_ints = 1;
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// map<string, OtherMessage> map_of_messages = 2;
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// }
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//
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// would have HCL like:
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//
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// map_of_ints = {
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// "foo": 1,
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// "bar": 2,
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// }
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// map_of_messages "foo" {
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// ...other fields
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// }
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// map_of_messages "bar" {
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// ...other fields
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// }
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//
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// Similar goes for list of primitives vs list of messages (except the block syntax uses no labels). The differences
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// between primitive fields outside of a collection and a message field really just amounts to not having to specify
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// the "=" between the field name and the "{" character.
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//
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// Field Mapping
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// | proto3 | HCL Type | example | notes |
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// |------------------------+---------------+---------+---------------------------------------------------------------------------------+
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// | message | Object | | Represented as a block |
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// | enum | String | | |
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// | map<K,V> | Map | | All keys are converted to/from strings. |
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// | repeated V | List | | |
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// | bool | Bool | | |
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// | string | String | | |
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// | bytes | base64 String | | |
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// | int32, fixed32, uint32 | Number | | |
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// | int64, fixed64, uint64 | Number | | |
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// | float, double | Number | | |
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//
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// ----- Well Known Types -----
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//
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// | Any | Object | | |
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// | Timestamp | String | | RFC 3339 compliant |
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// | Duration | String | | String form is what would be accepted by time.ParseDuration |
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// | Struct | Map | | |
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// | Empty | Object | | An object with no fields |
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// | BoolValue | Bool | | Mostly the same as a regular bool except null values in the HCL are preserved |
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// | BytesValue | Bytes | | Mostly the same as a regular bytes except null values in the HCL are preserved |
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// | StringValue | String | | Mostly the same as a regular string except null values in the HCL are preserved |
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// | FloatValue | Number | | Mostly the same as a regular float except null values in the HCL are preserved |
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// | DoubleValue | Number | | Mostly the same as a regular double except null values in the HCL are preserved |
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// | Int32Value | Number | | Mostly the same as a regular int32 except null values in the HCL are preserved |
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// | UInt32Value | Number | | Mostly the same as a regular uint32 except null values in the HCL are preserved |
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// | Int64Value | Number | | Mostly the same as a regular int64 except null values in the HCL are preserved |
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// | UInt64Value | Number | | Mostly the same as a regular uint64 except null values in the HCL are preserved |
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// | FieldMask | String | | Each string of the FieldMask will be joined with a '.' |
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//
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package protohcl
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