disable Pkg3 precompile unless opted into

stdlib/Pkg3/src/API.jl

@@ -7,7 +7,7 @@ import Dates
 import LibGit2
 
 import Pkg3
-import Pkg3: depots, logdir, devdir
+import Pkg3: depots, logdir, devdir, print_first_command_header
 using Pkg3.Types
 using Pkg3.TOML
 
@@ -19,6 +19,7 @@ add(pkgs::Vector{String}; kwargs...)      = add([PackageSpec(pkg) for pkg in pkg
 add(pkgs::Vector{PackageSpec}; kwargs...) = add(Context(), pkgs; kwargs...)
 
 function add(ctx::Context, pkgs::Vector{PackageSpec}; kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
     project_resolve!(ctx.env, pkgs)
@@ -33,6 +34,7 @@ rm(pkgs::Vector{String}; kwargs...)      = rm([PackageSpec(pkg) for pkg in pkgs]
 rm(pkgs::Vector{PackageSpec}; kwargs...) = rm(Context(), pkgs; kwargs...)
 
 function rm(ctx::Context, pkgs::Vector{PackageSpec}; kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
     project_resolve!(ctx.env, pkgs)
@@ -48,6 +50,7 @@ up(pkgs::Vector{PackageSpec}; kwargs...) = up(Context(), pkgs; kwargs...)
 
 function up(ctx::Context, pkgs::Vector{PackageSpec};
             level::UpgradeLevel=UPLEVEL_MAJOR, mode::PackageMode=PKGMODE_PROJECT, kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
 
@@ -126,6 +129,7 @@ pin(pkgs::Vector{String}; kwargs...)            = pin([PackageSpec(pkg) for pkg
 pin(pkgs::Vector{PackageSpec}; kwargs...)       = pin(Context(), pkgs; kwargs...)
 
 function pin(ctx::Context, pkgs::Vector{PackageSpec}; kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
     project_resolve!(ctx.env, pkgs)
@@ -139,6 +143,7 @@ free(pkgs::Vector{String}; kwargs...)            = free([PackageSpec(pkg) for pk
 free(pkgs::Vector{PackageSpec}; kwargs...)       = free(Context(), pkgs; kwargs...)
 
 function free(ctx::Context, pkgs::Vector{PackageSpec}; kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
     project_resolve!(ctx.env, pkgs)
@@ -155,6 +160,7 @@ checkout(pkgs::Vector{PackageSpec}; kwargs...)        = checkout([(pkg, nothing)
 checkout(pkgs_branches::Vector; kwargs...)            = checkout(Context(), pkgs_branches; kwargs...)
 
 function checkout(ctx::Context, pkgs_branches::Vector; path = devdir(), kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
     pkgs = [p[1] for p in pkgs_branches]
@@ -171,6 +177,7 @@ test(pkgs::Vector{String}; kwargs...)             = test([PackageSpec(pkg) for p
 test(pkgs::Vector{PackageSpec}; kwargs...)        = test(Context(), pkgs; kwargs...)
 
 function test(ctx::Context, pkgs::Vector{PackageSpec}; coverage=false, kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     ctx.preview && preview_info()
     project_resolve!(ctx.env, pkgs)
@@ -192,6 +199,7 @@ end
 
 
 function gc(ctx::Context=Context(); period = Dates.Week(6), kwargs...)
+    print_first_command_header()
     function recursive_dir_size(path)
         sz = 0
         for (root, dirs, files) in walkdir(path)
@@ -310,6 +318,7 @@ build(pkg::PackageSpec) = build([pkg])
 build(pkgs::Vector{PackageSpec}) = build(Context(), pkgs)
 
 function build(ctx::Context, pkgs::Vector{PackageSpec}; kwargs...)
+    print_first_command_header()
     Context!(ctx; kwargs...)
     if isempty(pkgs)
         for (name, infos) in ctx.env.manifest, info in infos
@@ -329,6 +338,7 @@ function build(ctx::Context, pkgs::Vector{PackageSpec}; kwargs...)
 end
 
 function init(path::String)
+    print_first_command_header()
     ctx = Context(env = EnvCache(joinpath(path, "Project.toml")))
     Pkg3.Operations.init(ctx)
 end

stdlib/Pkg3/src/Pkg3.jl

@@ -9,6 +9,23 @@ depots() = Base.DEPOT_PATH
 logdir() = joinpath(depots()[1], "logs")
 devdir() = get(ENV, "JULIA_PKG_DEVDIR", joinpath(homedir(), ".julia", "dev"))
 
+have_warned_session = false
+function print_first_command_header()
+    global have_warned_session
+    have_warned_session && return
+    @info """
+    Pkg3 is still under development, please file issues at `https://github.com/JuliaLang/Pkg3.jl`.
+    """
+    if !PKG3_IS_PRECOMPILED && !haskey(ENV, "JULIA_PKG3_DISABLE_PRECOMPILE_WARNING")
+        @info """
+        Pkg3 is running without precompile statements, first action will be slow.
+        Rebuild julia with the environment variable `JULIA_PKG3_PRECOMPILE` set to enable precompilation of PKG3.
+        This message can be disabled by setting the env variable `JULIA_PKG3_DISABLE_PRECOMPILE_WARNING`.
+        """
+    end
+    have_warned_session = true
+end
+
 # load snapshotted dependencies
 include("../ext/TOML/src/TOML.jl")
 
@@ -41,6 +58,13 @@ end
 using Pkg3.Types
 using UUIDs
 import LibGit2
-include("precompile.jl")
+# This crashes low memory systems and some of Julia's CI
+# so keep it disabled by default for now.
+if haskey(ENV, "JULIA_PKG3_PRECOMPILE")
+    const PKG3_IS_PRECOMPILED = true
+    include("precompile.jl")
+else
+    const PKG3_IS_PRECOMPILED = false
+end
 
 end # module

stdlib/Pkg3/src/REPLMode.jl

@@ -7,7 +7,7 @@ import REPL
 import REPL: LineEdit, REPLCompletions
 
 import Pkg3
-import Pkg3: devdir
+import Pkg3: devdir, print_first_command_header
 using Pkg3.Types
 using Pkg3.Display
 using Pkg3.Operations
@@ -151,6 +151,7 @@ const lex_re = r"^[\?\./\+\-](?!\-) | [^@\s]+\s*=\s*[^@\s]+ | @\s*[^@\s]* | [^@\
 const Token = Union{Command, Option, VersionRange, String}
 
 function tokenize(cmd::String)::Vector{Token}
+    print_first_command_header()
     tokens = Token[]
     words = map(m->m.match, eachmatch(lex_re, cmd))
     help_mode = false