Add Base.isrelocatable(pkg) (#53906)

This PR adds a utility function `isrelocatable(pkg)` that can be used to
check if `pkg` is already precompiled and if the associated cachefile is
relocatable.

The reason to implicitly perform the `isprecompiled` check is that the
exact same computation needs to be done to find the right `.ji`.

A `pkg` is said to be relocatable if
1. all `include()` paths are relocatable (they start with `@depot`),
2. all `include_dependency()` paths are relocatable (they start with
`@depot` and `track_content=true` was used to include them).

base/loading.jl

@@ -1678,25 +1678,13 @@ end
 # should sync with the types of arguments of `stale_cachefile`
 const StaleCacheKey = Tuple{Base.PkgId, UInt128, String, String}
 
-"""
-    Base.isprecompiled(pkg::PkgId; ignore_loaded::Bool=false)
-
-Returns whether a given PkgId within the active project is precompiled.
-
-By default this check observes the same approach that code loading takes
-with respect to when different versions of dependencies are currently loaded
-to that which is expected. To ignore loaded modules and answer as if in a
-fresh julia session specify `ignore_loaded=true`.
-
-!!! compat "Julia 1.10"
-    This function requires at least Julia 1.10.
-"""
-function isprecompiled(pkg::PkgId;
+function compilecache_path(pkg::PkgId;
         ignore_loaded::Bool=false,
         stale_cache::Dict{StaleCacheKey,Bool}=Dict{StaleCacheKey, Bool}(),
         cachepaths::Vector{String}=Base.find_all_in_cache_path(pkg),
         sourcepath::Union{String,Nothing}=Base.locate_package(pkg),
         flags::CacheFlags=CacheFlags())
+    path = nothing
     isnothing(sourcepath) && error("Cannot locate source for $(repr("text/plain", pkg))")
     for path_to_try in cachepaths
         staledeps = stale_cachefile(sourcepath, path_to_try, ignore_loaded = true, requested_flags=flags)
@@ -1728,10 +1716,64 @@ function isprecompiled(pkg::PkgId;
             # file might be read-only and then we fail to update timestamp, which is fine
             ex isa IOError || rethrow()
         end
-        return true
+        path = path_to_try
+        break
         @label check_next_path
     end
-    return false
+    return path
+end
+
+"""
+    Base.isprecompiled(pkg::PkgId; ignore_loaded::Bool=false)
+
+Returns whether a given PkgId within the active project is precompiled.
+
+By default this check observes the same approach that code loading takes
+with respect to when different versions of dependencies are currently loaded
+to that which is expected. To ignore loaded modules and answer as if in a
+fresh julia session specify `ignore_loaded=true`.
+
+!!! compat "Julia 1.10"
+    This function requires at least Julia 1.10.
+"""
+function isprecompiled(pkg::PkgId;
+        ignore_loaded::Bool=false,
+        stale_cache::Dict{StaleCacheKey,Bool}=Dict{StaleCacheKey, Bool}(),
+        cachepaths::Vector{String}=Base.find_all_in_cache_path(pkg),
+        sourcepath::Union{String,Nothing}=Base.locate_package(pkg),
+        flags::CacheFlags=CacheFlags())
+    path = compilecache_path(pkg; ignore_loaded, stale_cache, cachepaths, sourcepath, flags)
+    return !isnothing(path)
+end
+
+"""
+    Base.isrelocatable(pkg::PkgId)
+
+Returns whether a given PkgId within the active project is precompiled and the
+associated cache is relocatable.
+
+!!! compat "Julia 1.11"
+    This function requires at least Julia 1.11.
+"""
+function isrelocatable(pkg::PkgId)
+    path = compilecache_path(pkg)
+    isnothing(path) && return false
+    io = open(path, "r")
+    try
+        iszero(isvalid_cache_header(io)) && throw(ArgumentError("Invalid header in cache file $cachefile."))
+        _, (includes, includes_srcfiles, _), _... = _parse_cache_header(io, path)
+        for inc in includes
+            !startswith(inc.filename, "@depot") && return false
+            if inc ∉ includes_srcfiles
+                # its an include_dependency
+                track_content = inc.mtime == -1.0
+                track_content || return false
+            end
+        end
+    finally
+        close(io)
+    end
+    return true
 end
 
 # search for a precompile cache file to load, after some various checks
@@ -3064,7 +3106,7 @@ function resolve_depot(inc::AbstractString)
 end
 
 
-function parse_cache_header(f::IO, cachefile::AbstractString)
+function _parse_cache_header(f::IO, cachefile::AbstractString)
     flags = read(f, UInt8)
     modules = Vector{Pair{PkgId, UInt64}}()
     while true
@@ -3148,6 +3190,13 @@ function parse_cache_header(f::IO, cachefile::AbstractString)
 
     srcfiles = srctext_files(f, srctextpos, includes)
 
+    return modules, (includes, srcfiles, requires), required_modules, srctextpos, prefs, prefs_hash, clone_targets, flags
+end
+
+function parse_cache_header(f::IO, cachefile::AbstractString)
+    modules, (includes, srcfiles, requires), required_modules,
+        srctextpos, prefs, prefs_hash, clone_targets, flags = _parse_cache_header(f, cachefile)
+
     includes_srcfiles = CacheHeaderIncludes[]
     includes_depfiles = CacheHeaderIncludes[]
     for (i, inc) in enumerate(includes)

test/relocatedepot.jl

@@ -78,8 +78,10 @@ if !test_relocated_depot
             cachefiles = Base.find_all_in_cache_path(pkg)
             rm.(cachefiles, force=true)
             @test Base.isprecompiled(pkg) == false
+            @test Base.isrelocatable(pkg) == false # because not precompiled
             Base.require(pkg)
             @test Base.isprecompiled(pkg, ignore_loaded=true) == true
+            @test Base.isrelocatable(pkg) == true
         end
     end
 
@@ -93,10 +95,12 @@ if !test_relocated_depot
             rm.(cachefiles, force=true)
             rm(joinpath(@__DIR__, pkgname, "src", "foodir"), force=true, recursive=true)
             @test Base.isprecompiled(pkg) == false
+            @test Base.isrelocatable(pkg) == false # because not precompiled
             touch(joinpath(@__DIR__, pkgname, "src", "foo.txt"))
             mkdir(joinpath(@__DIR__, pkgname, "src", "foodir"))
             Base.require(pkg)
             @test Base.isprecompiled(pkg, ignore_loaded=true) == true
+            @test Base.isrelocatable(pkg) == false # because tracked by mtime
         end
     end
 
@@ -110,10 +114,12 @@ if !test_relocated_depot
             rm.(cachefiles, force=true)
             rm(joinpath(@__DIR__, pkgname, "src", "bardir"), force=true, recursive=true)
             @test Base.isprecompiled(pkg) == false
+            @test Base.isrelocatable(pkg) == false # because not precompiled
             touch(joinpath(@__DIR__, pkgname, "src", "bar.txt"))
             mkdir(joinpath(@__DIR__, pkgname, "src", "bardir"))
             Base.require(pkg)
             @test Base.isprecompiled(pkg, ignore_loaded=true) == true
+            @test Base.isrelocatable(pkg) == true
         end
     end
 
@@ -202,6 +208,7 @@ else
             # stdlib should be already precompiled
             pkg = Base.identify_package("DelimitedFiles")
             @test Base.isprecompiled(pkg) == true
+            @test Base.isrelocatable(pkg) == true
         end
     end
 
@@ -213,6 +220,7 @@ else
             push!(DEPOT_PATH, joinpath(@__DIR__, "relocatedepot", "julia")) # contains cache file
             pkg = Base.identify_package(pkgname)
             @test Base.isprecompiled(pkg) == true
+            @test Base.isrelocatable(pkg) == true
         end
     end
 
@@ -224,10 +232,13 @@ else
             push!(DEPOT_PATH, joinpath(@__DIR__, "relocatedepot", "julia")) # contains cache file
             pkg = Base.identify_package(pkgname)
             @test Base.isprecompiled(pkg) == false # moving depot changes mtime of include_dependency
+            @test Base.isrelocatable(pkg) == false # because not precompiled
             Base.require(pkg)
             @test Base.isprecompiled(pkg) == true
+            @test Base.isrelocatable(pkg) == false # because tracked by mtime
             touch(joinpath(@__DIR__, "relocatedepot", "RelocationTestPkg2", "src", "foodir", "foofoo"))
             @test Base.isprecompiled(pkg) == false
+            @test Base.isrelocatable(pkg) == false # because tracked by mtime
         end
     end
 
@@ -239,8 +250,10 @@ else
             push!(DEPOT_PATH, joinpath(@__DIR__, "relocatedepot", "julia")) # contains cache file
             pkg = Base.identify_package(pkgname)
             @test Base.isprecompiled(pkg) == true
+            @test Base.isrelocatable(pkg) == true
             touch(joinpath(@__DIR__, "relocatedepot", "RelocationTestPkg3", "src", "bardir", "barbar"))
             @test Base.isprecompiled(pkg) == false
+            @test Base.isrelocatable(pkg) == false # because not precompiled
         end
     end