add pathof(::Module)

NEWS.md

@@ -545,6 +545,8 @@ Library improvements
   * `Char` is now a subtype of `AbstractChar`, and most of the functions that
     take character arguments now accept any `AbstractChar` ([#26286]).
 
+  * `abspath(module)` returns the path a module was imported from ([#28310]).
+
   * `bytes2hex` now accepts an optional `io` argument to output to a hexadecimal stream
     without allocating a `String` first ([#27121]).
 

base/loading.jl

@@ -249,6 +249,20 @@ function locate_package(pkg::PkgId)::Union{Nothing,String}
 end
 locate_package(::Nothing) = nothing
 
+"""
+    abspath(m::Module)
+
+Return the path of `m.jl` file that was used to `import` module `m`,
+or `nothing` if `m` was not imported from a package.
+"""
+function Base.Filesystem.abspath(m::Module)
+    pkgid = get(Base.module_keys, m, nothing)
+    pkgid === nothing && return nothing
+    path = Base.locate_package(pkgid)
+    path === nothing && return nothing
+    return normpath(path)
+end
+
 ## generic project & manifest API ##
 
 const project_names = ("JuliaProject.toml", "Project.toml")

stdlib/Pkg/src/API.jl

@@ -429,13 +429,13 @@ function clone(url::String, name::String = "")
     develop(ctx, [parse_package(url)])
 end
 
-function dir(pkg::String, paths::String...)
-    @warn "Pkg.dir is only kept for legacy CI script reasons" maxlog=1
+function dir(pkg::String, paths::AbstractString...)
+    @warn "`Pkg.dir(pkgname, paths...)` is deprecated; instead, do `import $pkg; joinpath(dirname(abspath($pkg)), \"..\", paths...)`." maxlog=1
     pkgid = Base.identify_package(pkg)
-    pkgid == nothing && return nothing
+    pkgid === nothing && return nothing
     path = Base.locate_package(pkgid)
-    pkgid == nothing && return nothing
-    return joinpath(abspath(path, "..", "..", paths...))
+    path === nothing && return nothing
+    return abspath(path, "..", "..", paths...)
 end
 
 precompile() = precompile(Context())

test/loading.jl

@@ -218,6 +218,8 @@ Base.ACTIVE_PROJECT[] = nothing
     end
 end
 
+module NotPkgModule; end
+
 @testset "project & manifest import" begin
     @test !@isdefined Foo
     @test !@isdefined Bar
@@ -254,6 +256,12 @@ end
         end
     end
     @test Foo.which == "path"
+
+    @testset "abspath" begin
+        @test abspath(Foo) == normpath(abspath(@__DIR__, "project/deps/Foo1/src/Foo.jl"))
+        @test abspath(NotPkgModule) === nothing
+    end
+
 end
 
 ## systematic generation of test environments ##