automate julia install

(based on diffeqpy)

pyrms/__init__.py

@@ -1,16 +1,45 @@
-import os
-import subprocess
+import shutil
+from subprocess import run
+# juliacall must be loaded after `_ensure_julia_installed()` is run,
+# so this import is in `load_julia_packages()`
+# from juliacall import Main
 
-def install():
+def _find_julia():
+    return shutil.which("julia")
+
+def _ensure_julia_installed():
+    if not _find_julia():
+        print("No Julia version found. Installing Julia.")
+        run("juliaup update")
+        if not _find_julia():
+            raise RuntimeError(
+                "Julia installed with jill but `julia` binary cannot be found in the path"
+            )
+
+# TODO: upstream this function or an alternative into juliacall
+def load_julia_packages(*names):
     """
-    Install Julia packages required for diffeqpy.
+    Load Julia packages and return references to them, automatically installing julia and
+    the packages as necessary.
     """
-    import julia
-    import diffeqpy
-    julia.install()
-    diffeqpy.install()
-    from julia.api import Julia
-    jl = Julia(compiled_modules=False)
-    from julia import Pkg
-    Pkg.add("ReactionMechanismSimulator")
-    from julia import ReactionMechanismSimulator
+    # This is terrifying to many people. However, it seems SciML takes pragmatic approach.
+    _ensure_julia_installed()
+
+    script = """import Pkg
+    Pkg.activate(\"pyrms\", shared=true)
+    try
+        import {0}
+    catch e
+        e isa ArgumentError || throw(e)
+        Pkg.add([{1}])
+        import {0}
+    end
+    {0}""".format(", ".join(names), ", ".join(f'"{name}"' for name in names))
+
+    # Unfortunately, `seval` doesn't support multi-line strings
+    # https://github.com/JuliaPy/PythonCall.jl/issues/433
+    script = script.replace("\n", ";")
+
+    # Must be loaded after `_ensure_julia_installed()`
+    from juliacall import Main
+    return Main.seval(script)