Another attempt at an astable flag

src/macros.jl

@@ -282,11 +282,10 @@ macro byrow(args...)
     throw(ArgumentError("@byrow is deprecated outside of DataFramesMeta macros."))
 end
 
-
 """
     @passmissing(args...)
 
-Propograte missing values inside DataFramesMeta.jl macros.
+Propagrate missing values inside DataFramesMeta.jl macros.
 
 
 `@passmissing` is not a "real" Julia macro but rather serves as a "flag"
@@ -350,18 +349,24 @@ macro passmissing(args...)
     throw(ArgumentError("@passmissing only works inside DataFramesMeta macros."))
 end
 
+global astable_docstring_snippet = """
+    Transformations can also use the macro-flag `@astable` for creating multiple
+    new columns at once and letting transformations share the same name-space.
+    See `? @astable` for more details.
+    """
+
 """
     @astable(args...)
 
 Return a `NamedTuple` from a single transformation inside the DataFramesMeta.jl
 macros, `@select`, `@transform`, and their mutating and row-wise equivalents.
 
 `@astable` acts on a single block. It works through all top-level expressions
-and collects all such expressions of the form `:y = ...`, i.e. assignments to a
-`Symbol`, which is a syntax error outside of DataFramesMeta.jl macros. At the end of the
-expression, all assignments are collected into a `NamedTuple` to be used
-with the `AsTable` destination in the DataFrames.jl transformation
-mini-language.
+and collects all such expressions of the form `:y = ...` or `$(DOLLAR)y = ...`, i.e. assignments to a
+`Symbol` or an escaped column identifier, which is a syntax error outside of
+DataFramesMeta.jl macros. At the end of the expression, all assignments are collected
+into a `NamedTuple` to be used with the `AsTable` destination in the DataFrames.jl
+transformation mini-language.
 
 Concretely, the expressions
 
@@ -423,12 +428,22 @@ transformations. `@astable` solves this problem
     :new_col_2 = :new_col_1 + :z
 end
 
-Column assignment in `@astable` follows the same rules as
-column assignment more generally. Construct a new column
-from a string by escaping it with `$DOLLAR`, which can be a
-`Symbol` or an `AbstractString`. References to existing
-columns may be a `Symbol`, `AbstractString`, or an
-integer.
+Column assignment in `@astable` follows similar rules as
+column assignment in other DataFramesMeta.jl macros. The left-
+-hand-side of a column assignment can be either a `Symbol` or any
+expression which evaluates to a `Symbol` or `AbstractString`. For example
+`:y = ...`, and `$(DOLLAR)y = ...` are both valid ways of assigning a new column.
+However unlike other DataFramesMeta.jl macros, multi-column assignments via
+`AsTable` are disallowed. The following will fail.
+
+```
+@transform df @astable begin
+    $AsTable = :x
+end
+```
+
+References to existing columns also follow the same
+rules as other DataFramesMeta.jl macros.
 
 ### Examples
 
@@ -462,6 +477,8 @@ julia> @by df :a @astable begin
    1 │     1      5      6
    2 │     2     70     80
 
+julia> new_col = "New Column";
+
 julia> @rtransform df @astable begin
            f_a = first(:a)
            $(DOLLAR)new_col = :a + :b + f_a
@@ -1229,6 +1246,8 @@ transformations by row, `@transform` allows `@byrow` at the
 beginning of a block of transformations (i.e. `@byrow begin... end`).
 All transformations in the block will operate by row.
 
+$astable_docstring_snippet
+
 ### Examples
 
 ```jldoctest
@@ -1365,6 +1384,8 @@ transform!ations by row, `@transform!` allows `@byrow` at the
 beginning of a block of transform!ations (i.e. `@byrow begin... end`).
 All transform!ations in the block will operate by row.
 
+$astable_docstring_snippet
+
 ### Examples
 
 ```jldoctest
@@ -1477,6 +1498,8 @@ transformations by row, `@select` allows `@byrow` at the
 beginning of a block of selectations (i.e. `@byrow begin... end`).
 All transformations in the block will operate by row.
 
+$astable_docstring_snippet
+
 ### Examples
 
 ```jldoctest
@@ -1597,6 +1620,8 @@ transformations by row, `@select!` allows `@byrow` at the
 beginning of a block of select!ations (i.e. `@byrow begin... end`).
 All transformations in the block will operate by row.
 
+$astable_docstring_snippet
+
 ### Examples
 
 ```jldoctest
@@ -1713,6 +1738,8 @@ and
 @combine(df, :mx = mean(:x), :sx = std(:x))
 ```
 
+$astable_docstring_snippet
+
 ### Examples
 
 ```julia
@@ -1829,6 +1856,8 @@ and
 @by(df, :g, mx = mean(:x), sx = std(:x))
 ```
 
+$astable_docstring_snippet
+
 ### Examples
 
 ```julia

src/parsing.jl

@@ -109,7 +109,6 @@ function extract_macro_flags(ex::Expr, exprflags = deepcopy(DEFAULT_FLAGS))
             return (ex, exprflags)
         end
     end
-
     return (ex, exprflags)
 end
 
@@ -127,6 +126,9 @@ function check_macro_flags_consistency(exprflags)
         if !exprflags[BYROW_SYM][]
             s = "The `@passmissing` flag is currently only allowed with the `@byrow` flag"
             throw(ArgumentError(s))
+        elseif exprflags[ASTABLE_SYM][]
+            s = "The `@passmissing` flag is currently not allowed with the `@astable` flag"
+            throw(ArgumentError(s))
         end
     end
 end
@@ -224,6 +226,8 @@ function get_source_fun(function_expr; exprflags = deepcopy(DEFAULT_FLAGS))
         end
     end
 
+    println(MacroTools.prettify(fun))
+
     return source, fun
 end
 

src/parsing_astable.jl

@@ -54,10 +54,8 @@ end
 block(ex) = isexpr(ex, :block) ? ex : :($ex;)
 
 sym_or_str_to_sym(x::Union{AbstractString, Symbol}) = Symbol(x)
-function sym_or_str_to_sym(x)
-    e = "New columns created inside @astable must be Symbols or AbstractStrings"
-    throw(ArgumentError(e))
-end
+sym_or_str_to_sym(x) =
+    throw(ArgumentError("New columns created inside @astable must be Symbols or AbstractStrings"))
 
 function get_source_fun_astable(ex; exprflags = deepcopy(DEFAULT_FLAGS))
     inputs_to_function = Dict{Any, Symbol}()
@@ -88,6 +86,7 @@ function get_source_fun_astable(ex; exprflags = deepcopy(DEFAULT_FLAGS))
     inputargs = Expr(:tuple, values(inputs_to_function)...)
     nt_iterator = (:(DataFramesMeta.sym_or_str_to_sym($k) => $v) for (k, v) in lhs_assignments)
     nt_expr = Expr(:tuple, Expr(:parameters, nt_iterator...))
+
     body = Expr(:block, Expr(:block, exprs...), nt_expr)
 
     fun = quote

test/astable_flag.jl

@@ -11,7 +11,6 @@ const ≅ = isequal
 
     d = @rtransform df @astable begin
         :x = 1
-
         nothing
     end
 
@@ -42,10 +41,6 @@ const ≅ = isequal
     @test d == DataFrame(x = 5)
 end
 
-@testset "@astable with just assignments, mutating" begin
-    # After finalizing above testset
-end
-
 @testset "@astable with strings" begin
     df = DataFrame(a = 1, b = 2)
 
@@ -120,6 +115,49 @@ end
     @test d == DataFrame(x = 1, z = 6)
 end
 
+@testset "@astable with mutation" begin
+    df = DataFrame(a = 1, b = 2)
+
+    df2 = copy(df)
+    d = @rtransform! df2 @astable begin
+        :x = 1
+        nothing
+    end
+
+    @test d == DataFrame(a = 1, b = 2, x = 1)
+    @test d === df2
+
+    df2 = copy(df)
+    d = @rselect! df2 @astable begin
+        :x = 1
+        y = 100
+        nothing
+    end
+
+    @test d == DataFrame(x = 1)
+    @test d === df2
+
+    df2 = copy(df)
+    d = @transform! df2 @astable begin
+        :x = [5]
+        y = 100
+        nothing
+    end
+
+    @test d == DataFrame(a = 1, b = 2, x = 5)
+    @test d === df2
+
+    df2 = copy(df)
+    d = @select! df2 @astable begin
+        :x = [5]
+        y = 100
+        nothing
+    end
+
+    @test d == DataFrame(x = 5)
+    @test d === df2
+end
+
 @testset "grouping astable flag" begin
     df = DataFrame(a = [1, 1, 2, 2], b = [5, 6, 7, 8])
 
@@ -131,34 +169,43 @@ end
         :b_max = ex[2]
     end
 
-    @test sort(d.b_min) == [5, 7]
+    res_sorted = DataFrame(a = [1, 2], b_min = [5, 7], b_max = [6, 8])
+
+    @test sort(d, :b_min) == res_sorted
 
     d = @combine gd @astable begin
         ex = extrema(:b)
         $"b_min" = ex[1]
         $"b_max" = ex[2]
     end
 
-    @test sort(d.b_min) == [5, 7]
+    @test sort(d, :b_min) == res_sorted
 
     d = @by df :a @astable begin
         ex = extrema(:b)
         :b_min = ex[1]
         :b_max = ex[2]
     end
 
-    @test sort(d.b_min) == [5, 7]
+    @test sort(d, :b_min) == res_sorted
 
     d = @by df :a @astable begin
         ex = extrema(:b)
         $"b_min" = ex[1]
         $"b_max" = ex[2]
     end
 
-    @test sort(d.b_min) == [5, 7]
+    @test sort(d, :b_min) == res_sorted
 end
 
-
+@testset "errors with passmissing" begin
+    @eval df = DataFrame(y = 1)
+    @test_throws LoadError @eval @transform df @passmising @byrow @astable :x = 2
+    @test_throws LoadError @eval @transform df @byrow @astable @passmissing :x = 2
+    @test_throws LoadError @eval @transform df @astable @passmissing @byrow :x = 2
+    @test_throws LoadError @eval @rtransform df @astable @passmissing :x = 2
+    @test_throws LoadError @eval @rtransform df @passmissing @astable :x = 2
+end
 
 @testset "bad assignments" begin
     @eval df = DataFrame(y = 1)