gnu: Add julia-expat.

* gnu/packages/julia-xyz.scm (julia-expat-0.5.0): New variable.

gnu/packages/julia-xyz.scm

@@ -22,6 +22,7 @@
   #:use-module ((guix licenses) #:prefix license:)
   #:use-module (guix packages)
   #:use-module (gnu packages compression)
+  #:use-module (gnu packages xml)
   #:use-module (gnu packages tls))
 
 (define-public julia-uriparser
@@ -363,3 +364,40 @@ you expect,
     (synopsis "HTTP for Julia")
     (description "HTTP client and server functionality for Julia.")
     (license license:expat)))
+
+(define-public julia-libexpat
+  (package
+    (name "julia-libexpat")
+    ;; 0.6.0 requires julia 1.3+
+    (version "0.5.0")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/JuliaIO/LibExpat.jl")
+             (commit (string-append "v" version))))
+       (file-name "LibExpat")
+       (sha256
+        (base32 "1iny18z76bkf3yi6cvpfia7z1j7kn789iy0nwigsj2sb9mfi5x8b"))))
+    (arguments
+     `(#:phases
+       (modify-phases %standard-phases
+         (add-before 'precompile 'build-deps
+           (lambda*
+               (#:key outputs source inputs #:allow-other-keys)
+             (substitute*
+                 (string-append
+                  (assoc-ref outputs "out") "/share/julia/packages/"
+                  (strip-store-file-name source) "/src/LibExpat.jl")
+               (("const libexpat = \"libexpat\"")
+                (string-append "const libexpat = \""
+                               (assoc-ref inputs "expat")
+                               "/lib/libexpat.so\"")))
+             #t)))))
+    (propagated-inputs `(("julia-compat" ,julia-compat)
+                         ("expat" ,expat)))
+    (build-system julia-build-system)
+    (home-page "https://github.com/JuliaIO/LibExpat.jl")
+    (synopsis "Julia interface to the Expat XML parser library")
+    (description "Run XPath queries on fully parsed XML tree.")
+    (license license:expat)))