fix STDLIBS_BY_VERSION on non-latest version of Julia

(cherry picked from commit fd1820e)

src/Types.jl

@@ -363,6 +363,19 @@ function stdlibs()
 end
 is_stdlib(uuid::UUID) = uuid in keys(stdlibs())
 
+# Find the entry in `STDLIBS_BY_VERSION`
+# that corresponds to the requested version, and use that.
+function get_last_stdlibs(julia_version::VersionNumber)
+    last_stdlibs = Dict{UUID,String}()
+    for (version, stdlibs) in STDLIBS_BY_VERSION
+        if VersionNumber(julia_version.major, julia_version.minor, julia_version.patch) < version
+            break
+        end
+        last_stdlibs = stdlibs
+    end
+    return last_stdlibs
+end
+
 # Allow asking if something is an stdlib for a particular version of Julia
 function is_stdlib(uuid::UUID, julia_version::Union{VersionNumber, Nothing})
     # Only use the cache if we are asking for stdlibs in a custom Julia version
@@ -381,16 +394,7 @@ function is_stdlib(uuid::UUID, julia_version::Union{VersionNumber, Nothing})
         return false
     end
 
-    # If we are given an actual version, find the entry in `STDLIBS_BY_VERSION`
-    # that corresponds to the requested version, and use that.
-    last_stdlibs = Dict{UUID,String}()
-    for (version, stdlibs) in STDLIBS_BY_VERSION
-        if VersionNumber(julia_version.major, julia_version.minor, julia_version.patch) < version
-            break
-        end
-        last_stdlibs = stdlibs
-    end
-
+    last_stdlibs = get_last_stdlibs(julia_version)
     # Note that if the user asks for something like `julia_version = 0.7.0`, we'll
     # fall through with an empty `last_stdlibs`, which will always return `false`.
     return uuid in keys(last_stdlibs)

test/new.jl

@@ -2519,12 +2519,13 @@ using Pkg.Types: is_stdlib
 end
 
 @testset "STDLIBS_BY_VERSION up-to-date" begin
-    test_result = Pkg.Types.STDLIBS_BY_VERSION[end][2] == Pkg.Types.load_stdlib()
+    last_stdlibs = Pkg.Types.get_last_stdlibs(VERSION)
+    test_result = last_stdlibs == Pkg.Types.load_stdlib()
     if !test_result
         @error("STDLIBS_BY_VERSION out of date!  Manually fix given the info below, or re-run generate_historical_stdlibs.jl!")
-        @show length(Pkg.Types.STDLIBS_BY_VERSION[end][2]) length(Pkg.Types.load_stdlib())
-        @show setdiff(Pkg.Types.STDLIBS_BY_VERSION[end][2], Pkg.Types.load_stdlib())
-        @show setdiff(Pkg.Types.load_stdlib(), Pkg.Types.STDLIBS_BY_VERSION[end][2])
+        @show length(last_stdlibs) length(Pkg.Types.load_stdlib())
+        @show setdiff(last_stdlibs, Pkg.Types.load_stdlib())
+        @show setdiff(Pkg.Types.load_stdlib(), last_stdlibs)
     end
     @test test_result
 end