populate the dummy Pkg prompt properly

use Base.TOML.parse

stdlib/REPL/src/Pkg_beforeload.jl

@@ -0,0 +1,121 @@
+## Pkg stuff needed before Pkg has loaded
+
+const Pkg_pkgid = Base.PkgId(Base.UUID("44cfe95a-1eb2-52ea-b672-e2afdf69b78f"), "Pkg")
+const Pkg_REPLExt_pkgid = Base.PkgId(Base.UUID("ceef7b17-42e7-5b1c-81d4-4cc4a2494ccf"), "REPLExt")
+
+function load_pkg()
+    @lock Base.require_lock begin
+        REPLExt = Base.require_stdlib(Pkg_pkgid, "REPLExt")
+        # require_stdlib does not guarantee that the `__init__` of the package is done when loading is done async
+        # but we need to wait for the repl mode to be set up
+        lock = get(Base.package_locks, Pkg_REPLExt_pkgid.uuid, nothing)
+        lock !== nothing && wait(lock[2])
+        return REPLExt
+    end
+end
+
+## Below here copied/tweaked from Pkg Types.jl so that the dummy Pkg prompt
+# can populate the env correctly before Pkg loads
+
+function safe_realpath(path)
+    isempty(path) && return path
+    if ispath(path)
+        try
+            return realpath(path)
+        catch
+            return path
+        end
+    end
+    a, b = splitdir(path)
+    return joinpath(safe_realpath(a), b)
+end
+
+function find_project_file(env::Union{Nothing,String}=nothing)
+    project_file = nothing
+    if env isa Nothing
+        project_file = Base.active_project()
+        project_file === nothing && return nothing # in the Pkg version these are pkgerrors
+    elseif startswith(env, '@')
+        project_file = Base.load_path_expand(env)
+        project_file === nothing && return nothing
+    elseif env isa String
+        if isdir(env)
+            isempty(readdir(env)) || return nothing
+            project_file = joinpath(env, Base.project_names[end])
+        else
+            project_file = endswith(env, ".toml") ? abspath(env) :
+                abspath(env, Base.project_names[end])
+        end
+    end
+    @assert project_file isa String &&
+        (isfile(project_file) || !ispath(project_file) ||
+         isdir(project_file) && isempty(readdir(project_file)))
+    return safe_realpath(project_file)
+end
+
+function find_root_base_project(start_project::String)
+    project_file = start_project
+    while true
+        base_project_file = Base.base_project(project_file)
+        base_project_file === nothing && return project_file
+        project_file = base_project_file
+    end
+end
+
+function relative_project_path(project_file::String, path::String)
+    # compute path relative the project
+    # realpath needed to expand symlinks before taking the relative path
+    return relpath(safe_realpath(abspath(path)), safe_realpath(dirname(project_file)))
+end
+
+function projname(project_file::String)
+    p = Base.TOML.Parser()
+    Base.TOML.reinit!(p, read(project_file, String); filepath=project_file)
+    proj = Base.TOML.parse(p)
+    name = get(proj, "name", nothing)
+    if name === nothing
+        name = basename(dirname(project_file))
+    end
+    for depot in Base.DEPOT_PATH
+        envdir = joinpath(depot, "environments")
+        if startswith(abspath(project_file), abspath(envdir))
+            return "@" * name
+        end
+    end
+    return name
+end
+
+prev_project_file = nothing
+prev_project_timestamp = nothing
+prev_prefix = ""
+
+function Pkg_promptf()
+    global prev_project_timestamp, prev_prefix, prev_project_file
+    project_file = find_project_file()
+    prefix = ""
+    if project_file !== nothing
+        if prev_project_file == project_file && prev_project_timestamp == mtime(project_file)
+            prefix = prev_prefix
+        else
+            project_name = projname(project_file)
+            if project_name !== nothing
+                root = find_root_base_project(project_file)
+                rootname = projname(root)
+                if root !== project_file
+                    path_prefix = "/" * dirname(relative_project_path(root, project_file))
+                else
+                    path_prefix = ""
+                end
+                if textwidth(rootname) > 30
+                    rootname = first(rootname, 27) * "..."
+                end
+                prefix = "($(rootname)$(path_prefix)) "
+                prev_prefix = prefix
+                prev_project_timestamp = mtime(project_file)
+                prev_project_file = project_file
+            end
+        end
+    end
+    # Note no handling of Pkg.offline, as the Pkg version does here
+    return "$(prefix)pkg> "
+end

stdlib/REPL/src/REPL.jl

@@ -151,6 +151,8 @@ using .REPLCompletions
 include("TerminalMenus/TerminalMenus.jl")
 include("docview.jl")
 
+include("Pkg_beforeload.jl")
+
 @nospecialize # use only declared type signatures
 
 answer_color(::AbstractREPL) = ""
@@ -1082,19 +1084,6 @@ setup_interface(
     extra_repl_keymap::Any = repl.options.extra_keymap
 ) = setup_interface(repl, hascolor, extra_repl_keymap)
 
-const Pkg_pkgid = Base.PkgId(Base.UUID("44cfe95a-1eb2-52ea-b672-e2afdf69b78f"), "Pkg")
-const Pkg_REPLExt_pkgid = Base.PkgId(Base.UUID("ceef7b17-42e7-5b1c-81d4-4cc4a2494ccf"), "REPLExt")
-
-function load_pkg()
-    @lock Base.require_lock begin
-        REPLExt = Base.require_stdlib(Pkg_pkgid, "REPLExt")
-        # require_stdlib does not guarantee that the `__init__` of the package is done when loading is done async
-        # but we need to wait for the repl mode to be set up
-        lock = get(Base.package_locks, Pkg_REPLExt_pkgid.uuid, nothing)
-        lock !== nothing && wait(lock[2])
-        return REPLExt
-    end
-end
 
 # This non keyword method can be precompiled which is important
 function setup_interface(
@@ -1173,7 +1162,7 @@ function setup_interface(
 
     # Set up dummy Pkg mode that will be replaced once Pkg is loaded
     # use 6 dots to occupy the same space as the most likely "@v1.xx" env name
-    dummy_pkg_mode = Prompt("(......) $PKG_PROMPT",
+    dummy_pkg_mode = Prompt(Pkg_promptf,
         prompt_prefix = hascolor ? repl.pkg_color : "",
         prompt_suffix = hascolor ?
         (repl.envcolors ? Base.input_color : repl.input_color) : "",