Add and use isaccessiblefile for isfile_casesensitive (JuliaLang#…

…42922)

Fixes JuliaLang#42876

base/loading.jl

@@ -7,11 +7,11 @@ const require_lock = ReentrantLock()
 
 if Sys.isunix() && !Sys.isapple()
     # assume case-sensitive filesystems, don't have to do anything
-    isfile_casesensitive(path) = isfile(path)
+    isfile_casesensitive(path) = isaccessiblefile(path)
 elseif Sys.iswindows()
     # GetLongPathName Win32 function returns the case-preserved filename on NTFS.
     function isfile_casesensitive(path)
-        isfile(path) || return false  # Fail fast
+        isaccessiblefile(path) || return false  # Fail fast
         basename(Filesystem.longpath(path)) == basename(path)
     end
 elseif Sys.isapple()
@@ -44,7 +44,7 @@ elseif Sys.isapple()
     # Buffer buf;
     # getattrpath(path, &attr_list, &buf, sizeof(buf), FSOPT_NOFOLLOW);
     function isfile_casesensitive(path)
-        isfile(path) || return false
+        isaccessiblefile(path) || return false
         path_basename = String(basename(path))
         local casepreserved_basename
         header_size = 12
@@ -75,12 +75,41 @@ elseif Sys.isapple()
 else
     # Generic fallback that performs a slow directory listing.
     function isfile_casesensitive(path)
-        isfile(path) || return false
+        isaccessiblefile(path) || return false
         dir, filename = splitdir(path)
         any(readdir(dir) .== filename)
     end
 end
 
+# Check if the file is accessible. If stat fails return `false`
+
+function isaccessibledir(dir)
+    return try
+        isdir(dir)
+    catch err
+        err isa IOError || rethrow()
+        false
+    end
+end
+
+function isaccessiblefile(file)
+    return try
+        isfile(file)
+    catch err
+        err isa IOError || rethrow()
+        false
+    end
+end
+
+function isaccessiblepath(path)
+    return try
+        ispath(path)
+    catch err
+        err isa IOError || rethrow()
+        false
+    end
+end
+
 ## SHA1 ##
 
 struct SHA1

test/loading.jl

@@ -60,6 +60,12 @@ end
 @test Base.in_sysimage(Base.PkgId(Base.UUID("cf7118a7-6976-5b1a-9a39-7adc72f591a4"), "UUIDs"))
 @test Base.in_sysimage(Base.PkgId(Base.UUID("3a7fdc7e-7467-41b4-9f64-ea033d046d5b"), "NotAPackage")) == false
 
+## Unit tests for safe file operations ##
+
+@test Base.isaccessiblefile("/root/path/doesn't/exist") == false
+@test Base.isaccessiblepath("/root/path/doesn't/exist") == false
+@test Base.isaccessibledir("/root/path/doesn't/exist") == false
+
 # Issue #5789 and PR #13542:
 mktempdir() do dir
     cd(dir) do