Merge pull request #484 from JuliaLang/caf/tree-API-cleanup

Clean up and document syntax tree child access API + mark public API

Author: c42f

docs/src/api.md

@@ -124,13 +124,46 @@ JuliaSyntax.SHORT_FORM_FUNCTION_FLAG
 
 ## Syntax trees
 
-Syntax tree types:
+Access to the children of a tree node is provided by the functions
+
+```@docs
+JuliaSyntax.is_leaf
+JuliaSyntax.numchildren
+JuliaSyntax.children
+```
+
+For convenient access to the children, we also provide `node[i]`, `node[i:j]`
+and `node[begin:end]` by implementing `Base.getindex()`, `Base.firstindex()` and
+`Base.lastindex()`. We choose to return a view from `node[i:j]` to make it
+non-allocating.
+
+Tree traversal is supported by using these functions along with the predicates
+such as [`kind`](@ref) listed above.
+
+### Trees referencing the source
 
 ```@docs
 JuliaSyntax.SyntaxNode
-JuliaSyntax.GreenNode
 ```
 
-Functions applicable to syntax trees include everything in the sections on
+Functions applicable to `SyntaxNode` include everything in the sections on
 heads/kinds as well as the accessor functions in the source code handling
 section.
+
+### Relocatable syntax trees
+
+[`GreenNode`](@ref) is a special low level syntax tree: it's "relocatable" in
+the sense that it doesn't carry an absolute position in the source code or even
+a reference to the source text. This allows it to be reused for incremental
+parsing, but does make it a pain to work with directly!
+
+```@docs
+JuliaSyntax.GreenNode
+```
+
+Green nodes only have a relative position so implement `span()` instead of
+`byte_range()`:
+
+```@docs
+JuliaSyntax.span
+```

src/JuliaSyntax.jl

@@ -1,23 +1,81 @@
 module JuliaSyntax
 
-# Conservative list of exports - only export the most common/useful things
-# here.
+macro _public(syms)
+    if VERSION >= v"1.11"
+        names = syms isa Symbol ? [syms] : syms.args
+        esc(Expr(:public, names...))
+    else
+        nothing
+    end
+end
+
+# Public API, in the order of docs/src/api.md
+
+# Parsing.
+export parsestmt,
+    parseall,
+    parseatom
+
+@_public parse!,
+    ParseStream,
+    build_tree
 
-# Parsing. See also
-#   parse!(), ParseStream
-export parsestmt, parseall, parseatom
 # Tokenization
-export tokenize, Token, untokenize
-# Source file handling. See also
-#   highlight() sourcetext() source_line() source_location() char_range()
+export tokenize,
+    Token,
+    untokenize
+
+# Source file handling
+@_public sourcefile,
+    byte_range,
+    char_range,
+    first_byte,
+    last_byte,
+    filename,
+    source_line,
+    source_location,
+    sourcetext,
+    highlight
+
 export SourceFile
-# Expression heads/kinds. See also
-#   flags() and related predicates.
-export @K_str, kind, head
-# Syntax tree types. See also
-#   GreenNode
+@_public source_line_range
+
+# Expression predicates, kinds and flags
+export @K_str, kind
+@_public Kind
+
+@_public flags,
+    SyntaxHead,
+    head,
+    is_trivia,
+    is_prefix_call,
+    is_infix_op_call,
+    is_prefix_op_call,
+    is_postfix_op_call,
+    is_dotted,
+    is_suffixed,
+    is_decorated,
+    numeric_flags,
+    has_flags,
+    TRIPLE_STRING_FLAG,
+    RAW_STRING_FLAG,
+    PARENS_FLAG,
+    COLON_QUOTE,
+    TOPLEVEL_SEMICOLONS_FLAG,
+    MUTABLE_FLAG,
+    BARE_MODULE_FLAG,
+    SHORT_FORM_FUNCTION_FLAG
+
+# Syntax trees
+@_public is_leaf,
+    numchildren,
+    children
+
 export SyntaxNode
 
+@_public GreenNode,
+    span
+
 # Helper utilities
 include("utils.jl")
 

src/green_tree.jl

@@ -23,24 +23,58 @@ As implementation choices, we choose that:
 struct GreenNode{Head}
     head::Head
     span::UInt32
-    args::Union{Nothing,Vector{GreenNode{Head}}}
+    children::Union{Nothing,Vector{GreenNode{Head}}}
 end
 
-function GreenNode(head::Head, span::Integer, args=nothing) where {Head}
-    GreenNode{Head}(head, span, args)
+function GreenNode(head::Head, span::Integer, children=nothing) where {Head}
+    GreenNode{Head}(head, span, children)
 end
 
 # Accessors / predicates
-is_leaf(node::GreenNode)     = isnothing(node.args)
-children(node::GreenNode)    = isnothing(node.args) ? () : node.args
-span(node::GreenNode)        = node.span
+is_leaf(node::GreenNode)     = isnothing(node.children)
+children(node::GreenNode)    = node.children
+numchildren(node::GreenNode) = isnothing(node.children) ? 0 : length(node.children)
 head(node::GreenNode)        = node.head
 
+"""
+    span(node)
+
+Get the number of bytes this node covers in the source text.
+"""
+span(node::GreenNode) = node.span
+
+Base.getindex(node::GreenNode, i::Int) = children(node)[i]
+Base.getindex(node::GreenNode, rng::UnitRange) = view(children(node), rng)
+Base.firstindex(node::GreenNode) = 1
+Base.lastindex(node::GreenNode) = length(children(node))
+
+"""
+Get absolute position and span of the child of `node` at the given tree `path`.
+"""
+function child_position_span(node::GreenNode, path::Int...)
+    n = node
+    p = 1
+    for index in path
+        cs = children(n)
+        for i = 1:index-1
+            p += span(cs[i])
+        end
+        n = cs[index]
+    end
+    return n, p, n.span
+end
+
+function highlight(io::IO, source::SourceFile, node::GreenNode, path::Int...; kws...)
+    _, p, span = child_position_span(node, path...)
+    q = p + span - 1
+    highlight(io, source, p:q; kws...)
+end
+
 Base.summary(node::GreenNode) = summary(node.head)
 
-Base.hash(node::GreenNode, h::UInt) = hash((node.head, node.span, node.args), h)
+Base.hash(node::GreenNode, h::UInt) = hash((node.head, node.span, node.children), h)
 function Base.:(==)(n1::GreenNode, n2::GreenNode)
-    n1.head == n2.head && n1.span == n2.span && n1.args == n2.args
+    n1.head == n2.head && n1.span == n2.span && n1.children == n2.children
 end
 
 # Pretty printing

src/hooks.jl

@@ -45,11 +45,8 @@ function _incomplete_tag(n::SyntaxNode, codelen)
             return :none
         end
     end
-    if kind(c) == K"error" && begin
-                cs = children(c)
-                length(cs) > 0
-            end
-        for cc in cs
+    if kind(c) == K"error" && numchildren(c) > 0
+        for cc in children(c)
             if kind(cc) == K"error"
                 return :other
             end

src/syntax_tree.jl

@@ -106,10 +106,36 @@ function _to_SyntaxNode(source::SourceFile, txtbuf::Vector{UInt8}, offset::Int,
     end
 end
 
+"""
+    is_leaf(node)
+
+Determine whether the node is a leaf of the tree. In our trees a "leaf"
+corresponds to a single token in the source text.
+"""
 is_leaf(node::TreeNode) = node.children === nothing
-children(node::TreeNode) = (c = node.children; return c === nothing ? () : c)
+
+"""
+    children(node)
+
+Return an iterable list of children for the node. For leaves, return `nothing`.
+"""
+children(node::TreeNode) = node.children
+
+"""
+    numchildren(node)
+
+Return `length(children(node))` but possibly computed in a more efficient way.
+"""
 numchildren(node::TreeNode) = (isnothing(node.children) ? 0 : length(node.children))
 
+Base.getindex(node::AbstractSyntaxNode, i::Int) = children(node)[i]
+Base.getindex(node::AbstractSyntaxNode, rng::UnitRange) = view(children(node), rng)
+Base.firstindex(node::AbstractSyntaxNode) = 1
+Base.lastindex(node::AbstractSyntaxNode) = length(children(node))
+
+function Base.setindex!(node::SN, x::SN, i::Int) where {SN<:AbstractSyntaxNode}
+    children(node)[i] = x
+end
 
 """
     head(x)
@@ -217,10 +243,12 @@ 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, is_leaf(node) ? nothing : typeof(node)[], copy(node.data))
-    for child in children(node)
-        newchild = copy(child)
-        newchild.parent = newnode
-        push!(newnode, newchild)
+    if !is_leaf(node)
+        for child in children(node)
+            newchild = copy(child)
+            newchild.parent = newnode
+            push!(newnode, newchild)
+        end
     end
     return newnode
 end
@@ -235,71 +263,4 @@ function build_tree(::Type{SyntaxNode}, stream::ParseStream;
     SyntaxNode(source, green_tree, position=first_byte(stream), keep_parens=keep_parens)
 end
 
-#-------------------------------------------------------------------------------
-# Tree utilities
-
-"""
-    child(node, i1, i2, ...)
-
-Get child at a tree path. If indexing accessed children, it would be
-`node[i1][i2][...]`
-"""
-function child(node, path::Integer...)
-    n = node
-    for index in path
-        n = children(n)[index]
-    end
-    return n
-end
-
-function setchild!(node::SyntaxNode, path, x)
-    n1 = child(node, path[1:end-1]...)
-    n1.children[path[end]] = x
-end
-
-# We can overload multidimensional Base.getindex / Base.setindex! for node
-# types.
-#
-# The justification for this is to view a tree as a multidimensional ragged
-# array, where descending depthwise into the tree corresponds to dimensions of
-# the array.
-#
-# However... this analogy is only good for complete trees at a given depth (=
-# dimension). But the syntax is oh-so-handy!
-function Base.getindex(node::Union{SyntaxNode,GreenNode}, path::Int...)
-    child(node, path...)
-end
-function Base.lastindex(node::Union{SyntaxNode,GreenNode})
-    length(children(node))
-end
-
-function Base.setindex!(node::SyntaxNode, x::SyntaxNode, path::Int...)
-    setchild!(node, path, x)
-end
-
-"""
-Get absolute position and span of the child of `node` at the given tree `path`.
-"""
-function child_position_span(node::GreenNode, path::Int...)
-    n = node
-    p = 1
-    for index in path
-        cs = children(n)
-        for i = 1:index-1
-            p += span(cs[i])
-        end
-        n = cs[index]
-    end
-    return n, p, n.span
-end
-
-function child_position_span(node::SyntaxNode, path::Int...)
-    n = child(node, path...)
-    n, n.position, span(n)
-end
-
-function highlight(io::IO, source::SourceFile, node::GreenNode, path::Int...; kws...)
-    _, p, span = child_position_span(node, path...)
-    q = p + span - 1
-    highlight(io, source, p:q; kws...)
-end
+@deprecate haschildren(x) !is_leaf(x) false

test/green_node.jl

@@ -13,6 +13,15 @@
          SyntaxHead(K"Identifier", 0x0000)
     ]
 
+    @test numchildren(t) == 5
+    @test !is_leaf(t)
+    @test is_leaf(t[1])
+
+    @test t[1] === children(t)[1]
+    @test t[2:4] == [t[2],t[3],t[4]]
+    @test firstindex(t) == 1
+    @test lastindex(t) == 5
+
     t2 = parsestmt(GreenNode, "aa + b")
     @test t == t2
     @test t !== t2

test/runtests.jl

@@ -1,12 +1,6 @@
 using JuliaSyntax
 using Test
 
-using JuliaSyntax: SourceFile
-
-using JuliaSyntax: GreenNode, SyntaxNode,
-    flags, EMPTY_FLAGS, TRIVIA_FLAG, INFIX_FLAG,
-    children, child, setchild!, SyntaxHead
-
 include("test_utils.jl")
 include("test_utils_tests.jl")
 include("fuzz_test.jl")