From 73a52ff68748966f4e4dc318979b72dfe6415299 Mon Sep 17 00:00:00 2001
From: Koki Fushimi <paalon1936@gmail.com>
Date: Thu, 20 Jun 2024 12:35:04 +0900
Subject: [PATCH] Add objects to represent YAML versions.

Here we use abstract type & subtyping because it's common traits pattern
in Julia.
We do not need to export these objects because we can use strings for
versions in user-facing functions like:

```julia

function load(str::AbstractString; version::YAMLVersion)
    # ...
end

function load(str::AbstractString; version::AbstractString)
    version == "1.1" ? load(str, version=YAMLV1_1()) :
    version == "1.2" ? load(str, version=YAMLV1_2()) :
    throw(ErrorException())
end

load(str, version="1.1")
```
---
 src/YAML.jl     |  1 +
 src/versions.jl | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 src/versions.jl

diff --git a/src/YAML.jl b/src/YAML.jl
index 477239f..31a0274 100644
--- a/src/YAML.jl
+++ b/src/YAML.jl
@@ -27,6 +27,7 @@ using Dates
 using Printf
 using StringEncodings
 
+include("versions.jl")
 include("queue.jl")
 include("buffered_input.jl")
 include("tokens.jl")
diff --git a/src/versions.jl b/src/versions.jl
new file mode 100644
index 0000000..30b51c8
--- /dev/null
+++ b/src/versions.jl
@@ -0,0 +1,25 @@
+"""
+    YAMLVersion
+
+A type used for controlling the YAML version.
+
+Planned to be supported versions are:
+
+- [`YAMLV1_1`](@ref): YAML version 1.1
+- [`YAMLV1_2`](@ref): YAML version 1.2
+"""
+abstract type YAMLVersion end
+
+"""
+    YAMLV1_1
+
+A singleton type for YAML version 1.1.
+"""
+struct YAMLV1_1 <: YAMLVersion end
+
+"""
+    YAMLV1_2
+
+A singleton type for YAML version 1.2.
+"""
+struct YAMLV1_2 <: YAMLVersion end