Disable explicit return inside unknown macros

src/Runic.jl

@@ -138,6 +138,7 @@ mutable struct Context
     next_sibling::Union{Node, Nothing}
     # parent::Union{Node, Nothing}
     lineage_kinds::Vector{JuliaSyntax.Kind}
+    lineage_macros::Vector{String}
 end
 
 function Context(
@@ -168,11 +169,12 @@ function Context(
     call_depth = 0
     prev_sibling = next_sibling = nothing
     lineage_kinds = JuliaSyntax.Kind[]
+    lineage_macros = String[]
     format_on = true
     return Context(
         src_str, src_tree, src_io, fmt_io, fmt_tree, quiet, verbose, assert, debug, check,
         diff, filemode, indent_level, call_depth, format_on, prev_sibling, next_sibling,
-        lineage_kinds
+        lineage_kinds, lineage_macros
     )
 end
 
@@ -307,6 +309,9 @@ function format_node_with_kids!(ctx::Context, node::Node)
     ctx.prev_sibling = nothing
     ctx.next_sibling = nothing
     push!(ctx.lineage_kinds, kind(node))
+    if kind(node) === K"macrocall"
+        push!(ctx.lineage_macros, macrocall_name(ctx, node))
+    end
 
     # The new node parts. `kids′` aliases `kids` and only copied below if any of the
     # nodes change ("copy-on-write").
@@ -382,6 +387,9 @@ function format_node_with_kids!(ctx::Context, node::Node)
     ctx.prev_sibling = prev_sibling
     ctx.next_sibling = next_sibling
     pop!(ctx.lineage_kinds)
+    if kind(node) === K"macrocall"
+        pop!(ctx.lineage_macros)
+    end
     ctx.call_depth -= 1
     # Return a new node if any of the kids changed
     if any_kid_changed

src/chisels.jl

@@ -746,6 +746,53 @@ function kmatch(kids, kinds, i = firstindex(kids))
     return true
 end
 
+# Extract the macro name as written in the source.
+function macrocall_name(ctx, node)
+    @assert kind(node) === K"macrocall"
+    kids = verified_kids(node)
+    pred = x -> kind(x) in KSet"MacroName StringMacroName CmdMacroName core_@cmd"
+    mkind = kind(first_leaf_predicate(node, pred)::Node)
+    if kmatch(kids, KSet"@ MacroName")
+        p = position(ctx.fmt_io)
+        bytes = read(ctx.fmt_io, span(kids[1]) + span(kids[2]))
+        seek(ctx.fmt_io, p)
+        return String(bytes)
+    elseif kmatch(kids, KSet".") || kmatch(kids, KSet"CmdMacroName") ||
+            kmatch(kids, KSet"StringMacroName")
+        bytes = read_bytes(ctx, kids[1])
+        if mkind === K"CmdMacroName"
+            append!(bytes, "_cmd")
+        elseif mkind === K"StringMacroName"
+            append!(bytes, "_str")
+        end
+        return String(bytes)
+    elseif kmatch(kids, KSet"core_@cmd")
+        bytes = read_bytes(ctx, kids[1])
+        @assert length(bytes) == 0
+        return "core_@cmd"
+    else
+        # Don't bother looking in more complex expressions, just return unknown
+        return "<unknown macro>"
+    end
+end
+
+# Inserting `return` modifies the AST in a way that is visible to macros.. In general it is
+# never safe to change the AST inside a macro, but we make an exception for some common
+# "known" macros in order to be able to format functions that e.g. have an `@inline`
+# annotation in front.
+const MACROS_SAFE_TO_INSERT_RETURN = let set = Set{String}()
+    for m in ("inline", "noinline", "propagate_inbounds", "generated", "eval", "assume_effects")
+        push!(set, "@$m", "Base.@$m", "@Base.$m")
+    end
+    set
+end
+function safe_to_insert_return(ctx, node)
+    for m in ctx.lineage_macros
+        m in MACROS_SAFE_TO_INSERT_RETURN || return false
+    end
+    return true
+end
+
 ##########################
 # Utilities for IOBuffer #
 ##########################

src/runestone.jl

@@ -3513,6 +3513,9 @@ function explicit_return(ctx::Context, node::Node)
     if !(!is_leaf(node) && kind(node) in KSet"function macro do")
         return nothing
     end
+    if !safe_to_insert_return(ctx, node)
+        return nothing
+    end
     kids = verified_kids(node)
     pos = position(ctx.fmt_io)
     block_idx = findlast(x -> kind(x) === K"block", verified_kids(node))

test/runtests.jl

@@ -1261,6 +1261,15 @@ end
         for r in ("throw(ArgumentError())", "error(\"foo\")", "rethrow()")
             @test format_string("$f\n    $r\nend") == "$f\n    $r\nend"
         end
+        # Safe/known macros
+        @test format_string("@inline $f\n    x\nend") ==
+            "@inline $f\n    return x\nend"
+        @test format_string("Base.@noinline $f\n    x\nend") ==
+            "Base.@noinline $f\n    return x\nend"
+        @test format_string("@Base.eval $f\n    x\nend") ==
+            "@Base.eval $f\n    return x\nend"
+        # Unsafe/unknown macros
+        @test format_string("@kernel $f\n    x\nend") == "@kernel $f\n    x\nend"
         # `for` and `while` append `return nothing` to the end
         for r in ("for i in I\n    end", "while i in I\n    end")
             @test format_string("$f\n    $r\nend") == "$f\n    $r\n    return nothing\nend"
@@ -1374,7 +1383,7 @@ if Sys.isunix() && isdir(share_julia)
                             @warn "JuliaSyntax.ParseError for $path" err
                             @test_broken false
                         else
-                            @error "Error when formatting file $path"
+                            @error "Error when formatting file $path" err
                             @test false
                         end
                     end