add REPL hook to prompt to install missing packages, if available in …

…registry

src/Operations.jl

@@ -739,6 +739,43 @@ function download_source(ctx::Context; readonly=true)
     return Set{UUID}(entry.pkg.uuid for entry in pkgs_to_install)
 end
 
+function try_prompt_pkg_add(mods::Vector{Symbol})
+    ctx = Context()
+    available_uuids = [Types.registered_uuids(ctx.registries, String(mod)) for mod in mods] # vector of vectors
+    available_mods = mods[isempty.(available_uuids) .== false]
+    isempty(available_mods) && return false
+    resp = try
+        plural1 = length(mods) == 1 ? "" : "s"
+        plural2 = length(available_mods) == 1 ? "is" : "are"
+        missing_mod_list = length(mods) == 1 ? String(mods[1]) : "[$(join(mods, ", "))]"
+        available_mod_list = length(available_mods) == 1 ? repr(String(available_mods[1])) : repr(String.(available_mods))
+        println(ctx.io, " \033[32m\033[1m│\033[22m\033[0m Package$(plural1) $(missing_mod_list) not found,",
+                            " but $(available_mod_list) $(plural2) available from a registry.")
+        print(ctx.io, " \033[32m\033[1m│\033[22m\033[0m ")
+        if ctx.env.pkg !== nothing
+            printpkgstyle(ctx.io, :Project, string(ctx.env.pkg.name, " v", ctx.env.pkg.version, " ", pathrepr(Base.active_project())), true; color=Base.info_color())
+        else
+            printpkgstyle(ctx.io, :Project, pathrepr(Base.active_project()), true, color=Base.info_color())
+        end
+        Base.prompt(" \033[32m\033[1m└\033[22m\033[0m Add $(available_mod_list) to the active project and load? (y/n)", default = "n")
+    catch err
+        if err isa InterruptException
+            println()
+            return false
+        end
+        rethrow()
+    end
+    if lowercase(resp) in ["y", "yes"]
+        Pkg.add(string.(available_mods))
+        if length(available_mods) < length(mods)
+            return false # declare that some mods couldn't be installed
+        else
+            return true
+        end
+    end
+    return false
+end
+
 ################################
 # Manifest update and pruning #
 ################################

src/Pkg.jl

@@ -561,6 +561,7 @@ function __init__()
             end
         end
     end
+    push!(empty!(REPL.install_packages_hooks), Operations.try_prompt_pkg_add)
     OFFLINE_MODE[] = get(ENV, "JULIA_PKG_OFFLINE", nothing) == "true"
     return nothing
 end
@@ -671,6 +672,7 @@ const precompile_script = """
     Pkg.add("TestPkg")
     Pkg.develop(Pkg.PackageSpec(path="TestPkg.jl"))
     Pkg.add(Pkg.PackageSpec(path="TestPkg.jl/"))
+    Pkg.try_prompt_pkg_add(Symbol[:notapackage])
     ] add Te\t\t$CTRL_C
     ] st
     $CTRL_C