add option to create ext when adding weakdeps

src/Operations.jl

@@ -1677,9 +1677,33 @@ function add(ctx::Context, pkgs::Vector{PackageSpec}, new_git=Set{UUID}();
     else
         record_project_hash(ctx.env)
         write_env(ctx.env)
-        names_str = join(names, ", ")
+        names_str = join(names, ", ", " and ")
         printpkgstyle(ctx.io, :Added, "$names_str to [$(target)]")
     end
+    if target == :weakdeps
+        possible_extension_name = join(names) * "Ext"
+        if !haskey(ctx.env.project.exts, possible_extension_name)
+            plural = length(names) > 1 ? "these weak dependencies" : "this weak dependency"
+            printpkgstyle(
+                ctx.io,
+                :Option,
+                "Would you like to create a new entry for extension `$possible_extension_name` with $(plural)? ",
+                color=Base.info_color(),
+                newline=false
+            )
+            ans = if isinteractive()
+                Base.prompt(stdin, ctx.io, "[Y/n]")
+            else
+                "y"
+            end
+            if lowercase(ans) in ("y", "")
+                ctx.env.project.exts[possible_extension_name] = collect(names)
+                record_project_hash(ctx.env)
+                write_env(ctx.env)
+                printpkgstyle(ctx.io, :Created, "extension $possible_extension_name")
+            end
+        end
+    end
     return
 end
 

src/project.jl

@@ -241,18 +241,19 @@ function destructure(project::Project)::Dict
         should_delete(src) ? delete!(raw, key) : (raw[key] = src)
     end
 
-    entry!("name",     project.name)
-    entry!("uuid",     project.uuid)
-    entry!("version",  project.version)
+    entry!("name",      project.name)
+    entry!("uuid",      project.uuid)
+    entry!("version",   project.version)
     entry!("workspace", project.workspace)
-    entry!("manifest", project.manifest)
-    entry!("entryfile",     project.entryfile)
-    entry!("deps",     merge(project.deps, project._deps_weak))
-    entry!("weakdeps", project.weakdeps)
-    entry!("sources",  project.sources)
-    entry!("extras",   project.extras)
-    entry!("compat",   Dict(name => x.str for (name, x) in project.compat))
-    entry!("targets",  project.targets)
+    entry!("manifest",  project.manifest)
+    entry!("entryfile", project.entryfile)
+    entry!("deps",      merge(project.deps, project._deps_weak))
+    entry!("weakdeps",  project.weakdeps)
+    entry!("sources",   project.sources)
+    entry!("extras",    project.extras)
+    entry!("compat",    Dict(name => x.str for (name, x) in project.compat))
+    entry!("targets",   project.targets)
+    entry!("extensions", project.exts)
     return raw
 end
 

src/utils.jl

@@ -1,9 +1,10 @@
 
-function printpkgstyle(io::IO, cmd::Symbol, text::String, ignore_indent::Bool=false; color=:green)
+function printpkgstyle(io::IO, cmd::Symbol, text::String, ignore_indent::Bool=false; color=:green, newline::Bool=true)
     indent = textwidth(string(:Precompiling)) # "Precompiling" is the longest operation
     ignore_indent && (indent = 0)
     printstyled(io, lpad(string(cmd), indent), color=color, bold=true)
-    println(io, " ", text)
+    print(io, " ", text)
+    newline && println(io)
 end
 
 function linewrap(str::String; io = stdout_f(), padding = 0, width = Base.displaysize(io)[2])