Backports for 1.6, take 2.

src/API.jl

@@ -1321,7 +1321,7 @@ end
 instantiate(; kwargs...) = instantiate(Context(); kwargs...)
 function instantiate(ctx::Context; manifest::Union{Bool, Nothing}=nothing,
                      update_registry::Bool=true, verbose::Bool=false,
-                     platform::AbstractPlatform=HostPlatform(), allow_autoprecomp::Bool=true, kwargs...)
+                     platform::AbstractPlatform=HostPlatform(), allow_build::Bool=true, allow_autoprecomp::Bool=true, kwargs...)
     Context!(ctx; kwargs...)
     if !isfile(ctx.env.project_file) && isfile(ctx.env.manifest_file)
         _manifest = Pkg.Types.read_manifest(ctx.env.manifest_file)
@@ -1411,7 +1411,7 @@ function instantiate(ctx::Context; manifest::Union{Bool, Nothing}=nothing,
     end
     Operations.download_artifacts(ctx, art_pkgs; platform, verbose, io=ctx.io)
     # Run build scripts
-    Operations.build_versions(ctx, union(UUID[pkg.uuid for pkg in new_apply], new_git); verbose)
+    allow_build && Operations.build_versions(ctx, union(UUID[pkg.uuid for pkg in new_apply], new_git); verbose)
 
     allow_autoprecomp && Pkg._auto_precompile(ctx)
 end
@@ -1536,7 +1536,7 @@ function add_snapshot_to_undo(env=nothing)
         UndoState()
     end
     # Is the current state the same as the previous one, do nothing
-    if !isempty(state.entries) && env.project == env.original_project && env.manifest == env.original_manifest
+    if !isempty(state.entries) && env.project == env.original_project && env.manifest.deps == env.original_manifest.deps
         return
     end
     snapshot = UndoSnapshot(now(), env.project, env.manifest)

src/Operations.jl

@@ -361,10 +361,13 @@ end
 function resolve_versions!(ctx::Context, pkgs::Vector{PackageSpec})
     # compatibility
     if ctx.julia_version !== nothing
+        ctx.env.manifest.julia_version = ctx.julia_version
         v = intersect(ctx.julia_version, project_compatibility(ctx, "julia"))
         if isempty(v)
             @warn "julia version requirement for project not satisfied" _module=nothing _file=nothing
         end
+    else
+        ctx.env.manifest.julia_version = VERSION
     end
     names = Dict{UUID, String}(uuid => stdlib for (uuid, stdlib) in stdlibs())
     # recursive search for packages which are tracking a path
@@ -900,7 +903,7 @@ end
 
 function build(ctx::Context, pkgs::Vector{PackageSpec}, verbose::Bool)
     if any_package_not_installed(ctx) || !isfile(ctx.env.manifest_file)
-        Pkg.instantiate(ctx)
+        Pkg.instantiate(ctx, allow_build=false, allow_autoprecomp=false)
     end
     uuids = UUID[]
     _get_deps!(ctx, pkgs, uuids)

src/Types.jl

@@ -221,7 +221,7 @@ Base.:(==)(t1::PackageEntry, t2::PackageEntry) = t1.name == t2.name &&
 Base.hash(x::PackageEntry, h::UInt) = foldr(hash, [x.name, x.version, x.path, x.pinned, x.repo, x.tree_hash, x.deps], init=h)  # omits `other`
 
 Base.@kwdef mutable struct Manifest
-    julia_version::Union{Nothing,VersionNumber} = Base.VERSION
+    julia_version::Union{Nothing,VersionNumber} = nothing # only set to VERSION when resolving
     manifest_format::VersionNumber = v"1.0.0" # default to older flat format
     deps::Dict{UUID,PackageEntry} = Dict{UUID,PackageEntry}()
     other::Dict{String,Any} = Dict{String,Any}()

src/manifest.jl

@@ -129,7 +129,7 @@ function validate_manifest(julia_version::Union{Nothing,VersionNumber}, manifest
 end
 
 function Manifest(raw::Dict, f_or_io::Union{String, IO})::Manifest
-    julia_version = raw["julia_version"] == "nothing" ? nothing : VersionNumber(raw["julia_version"])
+    julia_version = haskey(raw, "julia_version") ? VersionNumber(raw["julia_version"]) : nothing
     manifest_format = VersionNumber(raw["manifest_format"])
     if !in(manifest_format.major, 1:2)
         if f_or_io isa IO
@@ -203,16 +203,16 @@ function read_manifest(f_or_io::Union{String,IO})
         pkgerror("Could not parse manifest: ", sprint(showerror, raw))
     end
     if is_v1_format_manifest(raw)
-        raw = convert_flat_format_manifest(raw)
+        raw = convert_v1_format_manifest(raw)
     end
     return Manifest(raw, f_or_io)
 end
 
-function convert_flat_format_manifest(old_raw_manifest::Dict)
+function convert_v1_format_manifest(old_raw_manifest::Dict)
     new_raw_manifest = Dict{String, Any}(
             "deps" => old_raw_manifest,
-            "julia_version" => "nothing", # must be a string here to match raw dict
             "manifest_format" => "1.0.0" # must be a string here to match raw dict
+            # don't set julia_version as it is unknown in old manifests
         )
     return new_raw_manifest
 end
@@ -239,7 +239,9 @@ function destructure(manifest::Manifest)::Dict
         raw = Dict{String,Vector{Dict{String,Any}}}()
     elseif manifest.manifest_format.major == 2
         raw = Dict{String,Any}()
-        raw["julia_version"] = manifest.julia_version
+        if !isnothing(manifest.julia_version) # don't write julia_version if nothing
+            raw["julia_version"] = manifest.julia_version
+        end
         raw["manifest_format"] = string(manifest.manifest_format.major, ".", manifest.manifest_format.minor)
         raw["deps"] = Dict{String,Vector{Dict{String,Any}}}()
         for (k, v) in manifest.other