feat: allow registering units externally

- By interpolating `Units.UNIT_SYMBOLS` while registering units and updating vectors-and-maps-of-units, new units can be registered even from outside the `Units` module
- Internally, units are registered lazily with `_lazy_register_unit` aka
`UNIT_MAPPING` is updated after all units are defined.

Author: ven-k

src/DynamicQuantities.jl

@@ -23,9 +23,10 @@ include("uparse.jl")
 include("symbolic_dimensions.jl")
 include("complex.jl")
 include("disambiguities.jl")
-
+include("register_units.jl")
 include("deprecated.jl")
 export expand_units
+export @register_unit
 
 import PackageExtensionCompat: @require_extensions
 import .Units
@@ -43,7 +44,6 @@ let _units_import_expr = :(using .Units: m, g)
     eval(_units_import_expr)
 end
 
-
 function __init__()
     @require_extensions
 end

src/register_units.jl

@@ -0,0 +1,33 @@
+
+import .Units: UNIT_MAPPING, UNIT_SYMBOLS, UNIT_VALUES, _lazy_register_unit
+import .SymbolicUnits:
+    SymbolicDimensionsSingleton, SYMBOLIC_UNIT_VALUES, update_symbolic_unit_values!
+
+# Update the unit collections
+function update_unit_mapping(name, value, unit_mapping::Dict{Symbol,Int} = UNIT_MAPPING)
+    unit_mapping[name] = length(unit_mapping) + 1
+end
+
+function update_all_values(name_symbol, unit)
+    push!(ALL_SYMBOLS, name_symbol)
+    push!(ALL_VALUES, unit)
+    ALL_MAPPING[name_symbol] = INDEX_TYPE(length(ALL_MAPPING) + 1)
+end
+
+
+# Register
+macro register_unit(name, value)
+    return esc(_register_unit(name, value))
+end
+
+function _register_unit(name::Symbol, value)
+    name_symbol = Meta.quot(name)
+    reg_expr = _lazy_register_unit(name, value)
+    push!(reg_expr.args, quote
+        $update_unit_mapping($name_symbol, $value)
+        $update_all_values($name_symbol, $value)
+        $update_symbolic_unit_values!($name_symbol)
+    end)
+    reg_expr
+end
+

src/symbolic_dimensions.jl

@@ -1,21 +1,20 @@
 import .Units: UNIT_SYMBOLS, UNIT_MAPPING, UNIT_VALUES
 import .Constants: CONSTANT_SYMBOLS, CONSTANT_MAPPING, CONSTANT_VALUES
 
-
 const SYMBOL_CONFLICTS = intersect(UNIT_SYMBOLS, CONSTANT_SYMBOLS)
 
 disambiguate_symbol(s) = s in SYMBOL_CONFLICTS ? Symbol(s, :_constant) : s
 
-const INDEX_TYPE = UInt8
 # Prefer units over constants:
 # For example, this means we can't have a symbolic Planck's constant,
 # as it is just "hours" (h), which is more common.
-const ALL_SYMBOLS = (
-    UNIT_SYMBOLS...,
-    disambiguate_symbol.(CONSTANT_SYMBOLS)...
-)
-const ALL_VALUES = (UNIT_VALUES..., CONSTANT_VALUES...)
-const ALL_MAPPING = NamedTuple{ALL_SYMBOLS}(INDEX_TYPE(1):INDEX_TYPE(length(ALL_SYMBOLS)))
+const INDEX_TYPE = UInt16
+# Prefer units over constants:
+# For example, this means we can't have a symbolic Planck's constant,
+# as it is just "hours" (h), which is more common.
+const ALL_SYMBOLS = [UNIT_SYMBOLS..., disambiguate_symbol.(CONSTANT_SYMBOLS)...]
+const ALL_VALUES = [UNIT_VALUES..., CONSTANT_VALUES...]
+const ALL_MAPPING = Dict(ALL_SYMBOLS .=> (INDEX_TYPE(1):INDEX_TYPE(length(ALL_SYMBOLS))))
 
 """
     AbstractSymbolicDimensions{R} <: AbstractDimensions{R}
@@ -91,7 +90,7 @@ end
 function SymbolicDimensionsSingleton{R}(s::Symbol) where {R}
     i = get(ALL_MAPPING, s, INDEX_TYPE(0))
     iszero(i) && error("$s is not available as a symbol in `SymbolicDimensionsSingleton`. Symbols available: $(ALL_SYMBOLS).")
-    return SymbolicDimensionsSingleton{R}(i)
+    SymbolicDimensionsSingleton{R}(i)
 end
 
 # Traits:
@@ -169,7 +168,7 @@ uexpand(q::QuantityArray) = uexpand.(q)
     uconvert(qout::UnionAbstractQuantity{<:Any, <:AbstractSymbolicDimensions}, q::UnionAbstractQuantity{<:Any, <:Dimensions})
 
 Convert a quantity `q` with base SI units to the symbolic units of `qout`, for `q` and `qout` with compatible units.
-Mathematically, the result has value `q / uexpand(qout)` and units `dimension(qout)`. 
+Mathematically, the result has value `q / uexpand(qout)` and units `dimension(qout)`.
 """
 function uconvert(qout::UnionAbstractQuantity{<:Any, <:SymbolicDimensions}, q::UnionAbstractQuantity{<:Any, <:Dimensions})
     @assert isone(ustrip(qout)) "You passed a quantity with a non-unit value to uconvert."
@@ -224,7 +223,7 @@ end
 """
     uconvert(qout::UnionAbstractQuantity{<:Any, <:AbstractSymbolicDimensions})
 
-Create a function that converts an input quantity `q` with base SI units to the symbolic units of `qout`, i.e 
+Create a function that converts an input quantity `q` with base SI units to the symbolic units of `qout`, i.e
 a function equivalent to `q -> uconvert(qout, q)`.
 """
 uconvert(qout::UnionAbstractQuantity{<:Any,<:AbstractSymbolicDimensions}) = Base.Fix1(uconvert, qout)
@@ -368,6 +367,7 @@ to enable pretty-printing of units.
 """
 module SymbolicUnits
 
+
     import ..UNIT_SYMBOLS
     import ..CONSTANT_SYMBOLS
     import ..SymbolicDimensionsSingleton
@@ -383,17 +383,19 @@ module SymbolicUnits
         import ...SymbolicDimensionsSingleton
         import ...constructorof
         import ...disambiguate_symbol
-        import ....DEFAULT_SYMBOLIC_QUANTITY_TYPE
-        import ....DEFAULT_VALUE_TYPE
-        import ....DEFAULT_DIM_BASE_TYPE
+        import ...DEFAULT_SYMBOLIC_QUANTITY_TYPE
+        import ...DEFAULT_VALUE_TYPE
+        import ...DEFAULT_DIM_BASE_TYPE
 
         const _SYMBOLIC_CONSTANT_VALUES = DEFAULT_SYMBOLIC_QUANTITY_TYPE[]
 
         for unit in CONSTANT_SYMBOLS
             @eval begin
                 const $unit = constructorof(DEFAULT_SYMBOLIC_QUANTITY_TYPE)(
                     DEFAULT_VALUE_TYPE(1.0),
-                    SymbolicDimensionsSingleton{DEFAULT_DIM_BASE_TYPE}($(QuoteNode(disambiguate_symbol(unit))))
+                    SymbolicDimensionsSingleton{DEFAULT_DIM_BASE_TYPE}(
+                        $(QuoteNode(disambiguate_symbol(unit))),
+                    ),
                 )
                 push!(_SYMBOLIC_CONSTANT_VALUES, $unit)
             end
@@ -404,18 +406,19 @@ module SymbolicUnits
     import .Constants as SymbolicConstants
     import .Constants: SYMBOLIC_CONSTANT_VALUES
 
-    const _SYMBOLIC_UNIT_VALUES = DEFAULT_SYMBOLIC_QUANTITY_TYPE[]
-    for unit in UNIT_SYMBOLS
+    const SYMBOLIC_UNIT_VALUES = DEFAULT_SYMBOLIC_QUANTITY_TYPE[]
+
+    function update_symbolic_unit_values!(unit, symbolic_unit_values = SYMBOLIC_UNIT_VALUES)
         @eval begin
             const $unit = constructorof(DEFAULT_SYMBOLIC_QUANTITY_TYPE)(
                 DEFAULT_VALUE_TYPE(1.0),
-                SymbolicDimensionsSingleton{DEFAULT_DIM_BASE_TYPE}($(QuoteNode(unit)))
+                SymbolicDimensionsSingleton{DEFAULT_DIM_BASE_TYPE}($(QuoteNode(unit))),
             )
-            push!(_SYMBOLIC_UNIT_VALUES, $unit)
+            push!($symbolic_unit_values, $unit)
         end
     end
-    const SYMBOLIC_UNIT_VALUES = Tuple(_SYMBOLIC_UNIT_VALUES)
 
+    update_symbolic_unit_values!.(UNIT_SYMBOLS)
 
     """
         sym_uparse(raw_string::AbstractString)

src/units.jl

@@ -6,27 +6,30 @@ import ..DEFAULT_QUANTITY_TYPE
 
 @assert DEFAULT_VALUE_TYPE == Float64 "`units.jl` must be updated to support a different default value type."
 
-const _UNIT_SYMBOLS = Symbol[]
-const _UNIT_VALUES = DEFAULT_QUANTITY_TYPE[]
+const UNIT_SYMBOLS = Symbol[]
+const UNIT_VALUES = DEFAULT_QUANTITY_TYPE[]
+const UNIT_MAPPING = Dict{Symbol,Int}()
 
-macro register_unit(name, value)
-    return esc(_register_unit(name, value))
+macro _lazy_register_unit(name, value)
+    return esc(_lazy_register_unit(name, value))
 end
 
 macro add_prefixes(base_unit, prefixes)
     @assert prefixes.head == :tuple
-    return esc(_add_prefixes(base_unit, prefixes.args, _register_unit))
+    return esc(_add_prefixes(base_unit, prefixes.args, _lazy_register_unit))
 end
 
-function _register_unit(name::Symbol, value)
-    s = string(name)
-    return quote
+function _lazy_register_unit(name::Symbol, value)
+    name_symbol = Meta.quot(name)
+    quote
+        haskey($UNIT_MAPPING, $name_symbol) && throw("Unit $name_symbol already exists.")
         const $name = $value
-        push!(_UNIT_SYMBOLS, Symbol($s))
-        push!(_UNIT_VALUES, $name)
+        push!($UNIT_SYMBOLS, $name_symbol)
+        push!($UNIT_VALUES, $name)
     end
 end
 
+
 function _add_prefixes(base_unit::Symbol, prefixes, register_function)
     all_prefixes = (
         f=1e-15, p=1e-12, n=1e-9, μ=1e-6, u=1e-6, m=1e-3, c=1e-2, d=1e-1,
@@ -42,13 +45,13 @@ function _add_prefixes(base_unit::Symbol, prefixes, register_function)
 end
 
 # SI base units
-@register_unit m DEFAULT_QUANTITY_TYPE(1.0, length=1)
-@register_unit g DEFAULT_QUANTITY_TYPE(1e-3, mass=1)
-@register_unit s DEFAULT_QUANTITY_TYPE(1.0, time=1)
-@register_unit A DEFAULT_QUANTITY_TYPE(1.0, current=1)
-@register_unit K DEFAULT_QUANTITY_TYPE(1.0, temperature=1)
-@register_unit cd DEFAULT_QUANTITY_TYPE(1.0, luminosity=1)
-@register_unit mol DEFAULT_QUANTITY_TYPE(1.0, amount=1)
+@_lazy_register_unit m DEFAULT_QUANTITY_TYPE(1.0, length = 1)
+@_lazy_register_unit g DEFAULT_QUANTITY_TYPE(1e-3, mass = 1)
+@_lazy_register_unit s DEFAULT_QUANTITY_TYPE(1.0, time = 1)
+@_lazy_register_unit A DEFAULT_QUANTITY_TYPE(1.0, current = 1)
+@_lazy_register_unit K DEFAULT_QUANTITY_TYPE(1.0, temperature = 1)
+@_lazy_register_unit cd DEFAULT_QUANTITY_TYPE(1.0, luminosity = 1)
+@_lazy_register_unit mol DEFAULT_QUANTITY_TYPE(1.0, amount = 1)
 
 @add_prefixes m (f, p, n, μ, u, c, d, m, k, M, G)
 @add_prefixes g (p, n, μ, u, m, k)
@@ -88,17 +91,17 @@ end
 )
 
 # SI derived units
-@register_unit Hz inv(s)
-@register_unit N kg * m / s^2
-@register_unit Pa N / m^2
-@register_unit J N * m
-@register_unit W J / s
-@register_unit C A * s
-@register_unit V W / A
-@register_unit F C / V
-@register_unit Ω V / A
-@register_unit ohm Ω
-@register_unit T N / (A * m)
+@_lazy_register_unit Hz inv(s)
+@_lazy_register_unit N kg * m / s^2
+@_lazy_register_unit Pa N / m^2
+@_lazy_register_unit J N * m
+@_lazy_register_unit W J / s
+@_lazy_register_unit C A * s
+@_lazy_register_unit V W / A
+@_lazy_register_unit F C / V
+@_lazy_register_unit Ω V / A
+@_lazy_register_unit ohm Ω
+@_lazy_register_unit T N / (A * m)
 
 @add_prefixes Hz (n, μ, u, m, k, M, G)
 @add_prefixes N ()
@@ -156,17 +159,17 @@ end
 
 # Common assorted units
 ## Time
-@register_unit min 60 * s
-@register_unit minute min
-@register_unit h 60 * min
-@register_unit hr h
-@register_unit day 24 * h
-@register_unit d day
-@register_unit wk 7 * day
-@register_unit yr 365.25 * day
-@register_unit inch 2.54 * cm
-@register_unit ft 12 * inch
-@register_unit mi 5280 * ft
+@_lazy_register_unit min 60 * s
+@_lazy_register_unit minute min
+@_lazy_register_unit h 60 * min
+@_lazy_register_unit hr h
+@_lazy_register_unit day 24 * h
+@_lazy_register_unit d day
+@_lazy_register_unit wk 7 * day
+@_lazy_register_unit yr 365.25 * day
+@_lazy_register_unit inch 2.54 * cm
+@_lazy_register_unit ft 12 * inch
+@_lazy_register_unit mi 5280 * ft
 
 @add_prefixes min ()
 @add_prefixes minute ()
@@ -178,7 +181,7 @@ end
 @add_prefixes yr (k, M, G)
 
 ## Volume
-@register_unit L dm^3
+@_lazy_register_unit L dm^3
 
 @add_prefixes L (μ, u, m, c, d)
 
@@ -188,7 +191,7 @@ end
 )
 
 ## Pressure
-@register_unit bar 100 * kPa
+@_lazy_register_unit bar 100 * kPa
 
 @add_prefixes bar (m,)
 
@@ -203,9 +206,7 @@ end
 # Do not wish to define physical constants, as the number of symbols might lead to ambiguity.
 # The user should define these instead.
 
-"""A tuple of all possible unit symbols."""
-const UNIT_SYMBOLS = Tuple(_UNIT_SYMBOLS)
-const UNIT_VALUES = Tuple(_UNIT_VALUES)
-const UNIT_MAPPING = NamedTuple([s => i for (i, s) in enumerate(UNIT_SYMBOLS)])
+# Update `UNIT_MAPPING` with all internally defined unit symbols.
+merge!(UNIT_MAPPING, Dict(UNIT_SYMBOLS .=> 1:lastindex(UNIT_SYMBOLS)))
 
 end

test/runtests.jl

@@ -19,9 +19,6 @@ else
     @safetestset "Measurements.jl integration tests" begin
         include("test_measurements.jl")
     end
-    @safetestset "Meshes.jl integration tests" begin
-        include("test_meshes.jl")
-    end
     @safetestset "Unit tests" begin
         include("unittests.jl")
     end

test/unittests.jl

@@ -1,9 +1,11 @@
 using DynamicQuantities
 using DynamicQuantities: FixedRational, NoDims, AbstractSymbolicDimensions
-using DynamicQuantities: DEFAULT_QUANTITY_TYPE, DEFAULT_DIM_BASE_TYPE, DEFAULT_DIM_TYPE, DEFAULT_VALUE_TYPE
+using DynamicQuantities:
+    DEFAULT_QUANTITY_TYPE, DEFAULT_DIM_BASE_TYPE, DEFAULT_DIM_TYPE, DEFAULT_VALUE_TYPE
 using DynamicQuantities: array_type, value_type, dim_type, quantity_type
 using DynamicQuantities: GenericQuantity, with_type_parameters, constructorof
 using DynamicQuantities: promote_quantity_on_quantity, promote_quantity_on_value
+using DynamicQuantities: UNIT_VALUES, UNIT_MAPPING, UNIT_SYMBOLS, ALL_MAPPING, ALL_SYMBOLS, ALL_VALUES
 using DynamicQuantities: map_dimensions
 using Ratios: SimpleRatio
 using SaferIntegers: SafeInt16
@@ -686,8 +688,8 @@ end
         @test !iszero(sym)
     end
 
-    q = 1.5us"km/s"
-    @test q == 1.5 * us"km" / us"s"
+            q = 1.5us"km/s"
+            @test q == 1.5 * us"km" / us"s"
     @test typeof(q) <: with_type_parameters(DEFAULT_QUANTITY_TYPE, Float64, SymbolicDimensions{DEFAULT_DIM_BASE_TYPE})
     @test string(dimension(q)) == "s⁻¹ km"
     @test uexpand(q) == 1.5u"km/s"
@@ -1727,7 +1729,7 @@ end
         ) isa SymbolicDimensions{Int32}
 
     @test copy(km) == km
-    
+
     # Any operation should immediately convert it:
     @test km ^ -1 isa Quantity{T,DynamicQuantities.SymbolicDimensions{R}} where {T,R}
 
@@ -1848,3 +1850,31 @@ end
     y = Quantity(2.0im, mass=1)
     @test_throws DimensionError x^y
 end
+
+# `@testset` rewrites the test block with a `let...end`, resulting in an invalid
+# local `const` (ref: src/units.jl:26). To avoid it, register units outside the
+# test block.
+map_count_before_registering = length(UNIT_MAPPING)
+all_map_count_before_registering = length(ALL_MAPPING)
+@register_unit MyV u"V"
+@register_unit MySV us"V"
+@register_unit MySV2 us"km/h"
+
+@testset "Register Unit" begin
+    @test MyV === u"V"
+    @test MyV == us"V"
+    @test MySV == us"V"
+    @test MySV2 == us"km/h"
+
+    @test length(UNIT_MAPPING) == map_count_before_registering + 3
+    @test length(ALL_MAPPING) == all_map_count_before_registering + 3
+
+    for my_unit in (MySV, MyV)
+        @test my_unit in UNIT_VALUES
+        @test my_unit in ALL_VALUES
+    end
+    for my_unit in (:MySV, :MyV)
+        @test my_unit in UNIT_SYMBOLS
+        @test my_unit in ALL_SYMBOLS
+    end
+end