From a6dee3c5e8d13e22b5dba1576c4cb41e614bbbdb Mon Sep 17 00:00:00 2001
From: Ian <i.r.butterworth@gmail.com>
Date: Tue, 29 Dec 2020 16:22:09 -0500
Subject: [PATCH] add REPL hook to prompt to install missing packages, if
 available in registry

---
 src/Pkg.jl               |  2 ++
 src/REPLMode/REPLMode.jl | 41 ++++++++++++++++++++++++++++++++++++++++
 test/repl.jl             |  5 +++++
 3 files changed, 48 insertions(+)

diff --git a/src/Pkg.jl b/src/Pkg.jl
index c37d42dfa4..462d2b7d38 100644
--- a/src/Pkg.jl
+++ b/src/Pkg.jl
@@ -561,6 +561,7 @@ function __init__()
             end
         end
     end
+    push!(empty!(REPL.install_packages_hooks), REPLMode.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.REPLMode.try_prompt_pkg_add(Symbol[:notapackage])
     ] add Te\t\t$CTRL_C
     ] st
     $CTRL_C
diff --git a/src/REPLMode/REPLMode.jl b/src/REPLMode/REPLMode.jl
index cc031bf75c..94ab979863 100644
--- a/src/REPLMode/REPLMode.jl
+++ b/src/REPLMode/REPLMode.jl
@@ -650,4 +650,45 @@ end
 
 const help = gen_help()
 
+function try_prompt_pkg_add(pkgs::Vector{Symbol})
+    ctx = Context()
+    available_uuids = [Types.registered_uuids(ctx.registries, String(pkg)) for pkg in pkgs] # vector of vectors
+    available_pkgs = pkgs[isempty.(available_uuids) .== false]
+    isempty(available_pkgs) && return false
+    resp = try
+        plural1 = length(pkgs) == 1 ? "" : "s"
+        plural2 = length(available_pkgs) == 1 ? "a package" : "packages"
+        plural3 = length(available_pkgs) == 1 ? "is" : "are"
+        plural4 = length(available_pkgs) == 1 ? "" : "s"
+        missing_pkg_list = length(pkgs) == 1 ? String(pkgs[1]) : "[$(join(pkgs, ", "))]"
+        available_pkg_list = length(available_pkgs) == 1 ? String(available_pkgs[1]) : "[$(join(available_pkgs, ", "))]"
+        printstyled(ctx.io, " │ "; color=:green)
+        println(ctx.io, "Package$(plural1) $(missing_pkg_list) not found,",
+                            " but $(plural2) named $(available_pkg_list) $(plural3) available from a registry.")
+        printstyled(ctx.io, " │ "; color=:green)
+        println(ctx.io, "Install package$(plural4)?")
+        printstyled(ctx.io, " │ "; color=:green)
+        print(ctx.io, "  ")
+        printstyled(ctx.io, REPLMode.promptf(); color=:blue)
+        println(ctx.io, "add ", join(available_pkgs, ' '))
+        printstyled(ctx.io, " └ "; color=:green)
+        Base.prompt(stdin, ctx.io, "(y/n)", default = "n")
+    catch err
+        if err isa InterruptException
+            println(ctx.io)
+            return false
+        end
+        rethrow()
+    end
+    if lowercase(resp) in ["y", "yes"]
+        Pkg.add(string.(available_pkgs))
+        if length(available_pkgs) < length(pkgs)
+            return false # declare that some pkgs couldn't be installed
+        else
+            return true
+        end
+    end
+    return false
+end
+
 end #module
diff --git a/test/repl.jl b/test/repl.jl
index d29f2d3183..30cb541845 100644
--- a/test/repl.jl
+++ b/test/repl.jl
@@ -667,4 +667,9 @@ end
     @inferred Pkg.REPLMode.CompoundSpecs(Pair{String,Vector{Pkg.REPLMode.CommandDeclaration}}[])
 end
 
+@testset "REPL missing package install hook" begin
+    @test Pkg.REPLMode.try_prompt_pkg_add(Symbol[:notapackage]) == false
+    # cannot test installation of findable packages given requires user input to stdin on the prompt
+end
+
 end # module