fix: make it a preference, not a fix

Author: IanButterworth

src/Operations.jl

@@ -903,9 +903,9 @@ function maybe_print_preferred_loaded_note(io::IO, direct_names::Vector{String},
     end
     joined = length(parts) == 2 ? string(parts[1], " and ", parts[2]) : parts[1]
     msg = if length(direct_names) + indirect_count > 1
-        "Preferring versions of $(joined) that are already loaded"
+        "was able to add the versions of $(joined) that are already loaded"
     else
-        "Preferring the version of $(joined) that is already loaded"
+        "was able to add the version of $(joined) that is already loaded"
     end
     printpkgstyle(io, :Resolve, msg; color = Base.info_color())
     return
@@ -2155,34 +2155,43 @@ function tiered_resolve(
         env::EnvCache, registries::Vector{Registry.RegistryInstance}, pkgs::Vector{PackageSpec}, julia_version,
         try_all_installed::Bool; preferred_versions::Dict{UUID, VersionNumber} = Dict{UUID, VersionNumber}()
     )
+    if !isempty(preferred_versions)
+        # first try maintaining any loaded versions of the new packages
+        try # do not modify existing subgraph
+            @debug "tiered_resolve: trying PRESERVE_ALL with any loaded versions of new packages"
+            return targeted_resolve(env, registries, pkgs, PRESERVE_ALL, julia_version; preferred_versions)
+        catch err
+            err isa Resolve.ResolverError || rethrow()
+        end
+    end
     if try_all_installed
         try # do not modify existing subgraph and only add installed versions of the new packages
             @debug "tiered_resolve: trying PRESERVE_ALL_INSTALLED"
-            return targeted_resolve(env, registries, pkgs, PRESERVE_ALL_INSTALLED, julia_version; preferred_versions)
+            return targeted_resolve(env, registries, pkgs, PRESERVE_ALL_INSTALLED, julia_version)
         catch err
             err isa Resolve.ResolverError || rethrow()
         end
     end
     try # do not modify existing subgraph
         @debug "tiered_resolve: trying PRESERVE_ALL"
-        return targeted_resolve(env, registries, pkgs, PRESERVE_ALL, julia_version; preferred_versions)
+        return targeted_resolve(env, registries, pkgs, PRESERVE_ALL, julia_version)
     catch err
         err isa Resolve.ResolverError || rethrow()
     end
     try # do not modify existing direct deps
         @debug "tiered_resolve: trying PRESERVE_DIRECT"
-        return targeted_resolve(env, registries, pkgs, PRESERVE_DIRECT, julia_version; preferred_versions)
+        return targeted_resolve(env, registries, pkgs, PRESERVE_DIRECT, julia_version)
     catch err
         err isa Resolve.ResolverError || rethrow()
     end
     try
         @debug "tiered_resolve: trying PRESERVE_SEMVER"
-        return targeted_resolve(env, registries, pkgs, PRESERVE_SEMVER, julia_version; preferred_versions)
+        return targeted_resolve(env, registries, pkgs, PRESERVE_SEMVER, julia_version)
     catch err
         err isa Resolve.ResolverError || rethrow()
     end
     @debug "tiered_resolve: trying PRESERVE_NONE"
-    return targeted_resolve(env, registries, pkgs, PRESERVE_NONE, julia_version; preferred_versions)
+    return targeted_resolve(env, registries, pkgs, PRESERVE_NONE, julia_version)
 end
 
 function targeted_resolve(

src/Resolve/maxsum.jl

@@ -1,7 +1,10 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 const DEFAULT_MAX_TIME = "300"
-const PREFERRED_VERSION_WEIGHT_BONUS = VersionWeight(typemax(Int32))
+# Prefer loaded versions, but not so strongly that it overrides compatibility constraints.
+# This bonus is added to the version weight of already-loaded packages, making them more
+# favorable than other versions but not creating hard requirements.
+const PREFERRED_VERSION_WEIGHT_BONUS = VersionWeight(100, 0, 0)
 
 # Some parameters to drive the decimation process
 mutable struct MaxSumParams

test/new.jl

@@ -3935,7 +3935,7 @@ end
         Pkg.activate(; temp = true)
         Pkg.add("Example", io = io) # v0.5.5 exists, but v0.5.4 is loaded
         add_output = String(take!(io))
-        @test occursin("Preferring the version of Example that is already loaded", add_output)
+        @test occursin("was able to add the version of Example that is already loaded", add_output)
         @test occursin("[7876af07] + Example v0.5.4", add_output)
         """
         cmd = addenv(

test/registry.jl

@@ -431,13 +431,13 @@ end
         # Tests that [email protected] does not get installed
         temp_pkg_dir() do env
             Pkg.Registry.add(url = "https://github.com/JuliaRegistries/Test")
-            Pkg.add("Example"; prefer_loaded_versions = false)
+            Pkg.add("Example")
             @test manifest_info(EnvCache().manifest, uuid).version == v"0.5.0"
             Pkg.update() # should not update Example
             @test manifest_info(EnvCache().manifest, uuid).version == v"0.5.0"
             @test_throws Pkg.Resolve.ResolverError Pkg.add(PackageSpec(name = "Example", version = v"0.5.1"))
             Pkg.rm("Example")
-            Pkg.add("JSON"; prefer_loaded_versions = false) # depends on Example
+            Pkg.add("JSON") # depends on Example
             @test manifest_info(EnvCache().manifest, uuid).version == v"0.5.0"
             Pkg.update()
             @test manifest_info(EnvCache().manifest, uuid).version == v"0.5.0"