Support copy for TreeNodes (#210)

Co-authored-by: c42f <[email protected]>

Author: timholy

src/syntax_tree.jl

@@ -244,6 +244,21 @@ function Base.push!(node::SN, child::SN) where SN<:AbstractSyntaxNode
     push!(args, child)
 end
 
+function Base.copy(node::TreeNode)
+    # copy the container but not the data (ie, deep copy the tree, shallow copy the data). copy(::Expr) is similar
+    # copy "un-parents" the top-level `node` that you're copying
+    newnode = typeof(node)(nothing, haschildren(node) ? typeof(node)[] : nothing, copy(node.data))
+    for child in children(node)
+        newchild = copy(child)
+        newchild.parent = newnode
+        push!(newnode, newchild)
+    end
+    return newnode
+end
+
+# shallow-copy the data
+Base.copy(data::SyntaxData) = SyntaxData(data.source, data.raw, data.position, data.val)
+
 function build_tree(::Type{SyntaxNode}, stream::ParseStream; filename=nothing, first_line=1, kws...)
     green_tree = build_tree(GreenNode, stream; kws...)
     source = SourceFile(sourcetext(stream), filename=filename, first_line=first_line)

test/syntax_tree.jl

@@ -36,6 +36,14 @@
     e = try node.val = :q catch e e end
     @test occursin("immutable", e.msg) && occursin("SyntaxData", e.msg)
 
+    # copy
+    t = parse(SyntaxNode, "a*b + c")
+    ct = copy(t)
+    ct.data = nothing
+    @test ct.data === nothing && t.data !== nothing
+    @test child(ct, 1).parent === ct
+    @test child(ct, 1) !== child(t, 1)
+
     node = parse(SyntaxNode, "f()")
     push!(node, parse(SyntaxNode, "x"))
     @test length(children(node)) == 2