WIP: Add DataFrames as a weak dependency

Project.toml

@@ -13,12 +13,15 @@ SnoopPrecompile = "66db9d55-30c0-4569-8b51-7e840670fc0c"
 SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 
 [weakdeps]
+DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 DimensionalData = "0703355e-b756-11e9-17c0-8b28908087d0"
 
 [extensions]
+JuMPDataFramesExt = "DataFrames"
 JuMPDimensionalDataExt = "DimensionalData"
 
 [compat]
+DataFrames = "1"
 DimensionalData = "0.24"
 MathOptInterface = "1.18"
 MutableArithmetics = "1"
@@ -27,8 +30,9 @@ SnoopPrecompile = "1"
 julia = "1.6"
 
 [extras]
+DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 DimensionalData = "0703355e-b756-11e9-17c0-8b28908087d0"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["DimensionalData", "Test"]
+test = ["DataFrames", "DimensionalData", "Test"]

ext/JuMPDataFramesExt.jl

@@ -0,0 +1,27 @@
+#  Copyright 2017, Iain Dunning, Joey Huchette, Miles Lubin, and contributors
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+module JuMPDataFramesExt
+
+import DataFrames
+import JuMP
+
+function JuMP.Containers.container(
+    f::F,
+    indices::Union{
+        JuMP.Containers.VectorizedProductIterator,
+        JuMP.Containers.NestedIterator,
+    },
+    ::Type{DataFrames.DataFrame},
+    names::AbstractVector,
+) where {F<:Function}
+    rows = vec(collect(indices))
+    data = [name => getindex.(rows, i) for (i, name) in enumerate(names)]
+    df = DataFrames.DataFrame(data)
+    df.value = map(i -> f(i...), rows)
+    return df
+end
+
+end #module

ext/test_DataFrames.jl

@@ -0,0 +1,21 @@
+#  Copyright 2017, Iain Dunning, Joey Huchette, Miles Lubin, and contributors
+#  This Source Code Form is subject to the terms of the Mozilla Public
+#  License, v. 2.0. If a copy of the MPL was not distributed with this
+#  file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+module TestContainersDataFrames
+
+using Test
+
+using DataFrames
+using JuMP
+
+function test_dimension_data_variable()
+    model = Model()
+    @variable(model, x[i = 2:4, j = 1:2], container = DataFrame)
+    @variable(model, y[i = 2:4, j = 1:2; isodd(i+j)], container = DataFrame)
+
+    return
+end
+
+end