Add integration test for CI and fix JuMP (#160)

Author: odow

.github/workflows/downstream.yml

@@ -0,0 +1,45 @@
+name: JuMP-integration
+on:
+  push:
+    branches: [master]
+  pull_request:
+    types: [opened, synchronize, reopened]
+jobs:
+  test:
+    name: Julia ${{ matrix.julia-version }} - ${{ matrix.package.repo }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        julia-version: ['1.6', '1']
+        os: ['ubuntu-latest']
+        package:
+          - {user: jump-dev, repo: JuMP.jl}
+    steps:
+      - uses: actions/checkout@v2
+      - uses: julia-actions/setup-julia@v1
+        with:
+          version: ${{ matrix.julia-version }}
+          arch: x64
+      - uses: julia-actions/julia-buildpkg@latest
+      - name: Clone Downstream
+        uses: actions/checkout@v2
+        with:
+          repository: ${{ matrix.package.user }}/${{ matrix.package.repo }}
+          path: downstream
+      - name: Load this and run the downstream tests
+        shell: julia --color=yes --project=downstream {0}
+        run: |
+          using Pkg
+          try
+            # force it to use this PR's version of the package
+            Pkg.develop(PackageSpec(path="."))  # resolver may fail with main deps
+            Pkg.update()
+            Pkg.test()  # resolver may fail with test time deps
+          catch err
+            err isa Pkg.Resolve.ResolverError || rethrow()
+            # If we can't resolve that means this is incompatible by SemVer and this is fine
+            # It means we marked this as a breaking change, so we don't need to worry about
+            # Mistakenly introducing a breaking change, as we have intentionally made one
+            @info "Not compatible with this release. No problem." exception=err
+            exit(0)  # Exit immediately, as a success
+          end

src/broadcast.jl

@@ -89,7 +89,7 @@ function broadcast_mutability(x, op, args::Vararg{Any,N}) where {N}
     return broadcast_mutability(typeof(x), op, typeof.(args)...)
 end
 
-_checked_size(s, x::AbstractArray) = size(x) == s
+_checked_size(s, x::AbstractArray) = length(x) == s
 _checked_size(::Any, ::Any) = true
 _checked_size(::Any, ::Tuple{}) = true
 function _checked_size(s, x::Tuple)
@@ -102,13 +102,15 @@ end
 # happen during broadcasting since we'll either need to return a different size
 # to `x`, or multiple copies of an argument will be used for different parts of
 # `x`. To simplify, let's just return `IsNotMutable` if the sizes are different,
-# which will be slower but correct.
+# which will be slower but correct. This is slightly complicated by the fact
+# that some AbstractArray do not support `size`, so we check with `length`
+# instead. If the `size`s are different, a later error will be thrown.
 function broadcast_mutability(
     x::AbstractArray,
     op,
     args::Vararg{Any,N},
 ) where {N}
-    if !_checked_size(size(x), args)::Bool
+    if !_checked_size(length(x), args)::Bool
         return IsNotMutable()
     end
     return broadcast_mutability(typeof(x), op, typeof.(args)...)