Check for path errors eagerly during load/save (#263) (#265)

* add missing gzip test file (and parent csv file)

* add eager checks for file and path existence

* create dummy file for multierr test

* add tests for path errors

* mkpath eagerly during save if dir doesn't exist

Author: IanButterworth

src/loadsave.jl

@@ -167,6 +167,9 @@ for fn in (:load, :loadstreaming, :metadata)
             isfile(filename(q)) || open(filename(q))  # force systemerror
             throw(UnknownFormat(q))
         end
+        if q isa File
+            !isfile(filename(q)) && throw(ArgumentError("No file exists at given path: $(filename(q))"))
+        end
         libraries = applicable_loaders(q)
         failures  = Any[]
         for library in libraries
@@ -191,6 +194,10 @@ for fn in (:save, :savestreaming)
     gen2_func_name = Symbol("fileio_", fn)
     @eval function $fn(@nospecialize(q::Formatted), @nospecialize(data...); @nospecialize(options...))
         unknown(q) && throw(UnknownFormat(q))
+        if q isa File
+            isdir(filename(q)) && throw(ArgumentError("Given file path is a directory: $(filename(q))"))
+            !isdir(dirname(filename(q))) && mkpath(dirname(filename(q)))
+        end
         libraries = applicable_savers(q)
         failures  = Any[]
         for library in libraries

test/error_handling.jl

@@ -1,5 +1,27 @@
 println("these tests will print warnings: ")
 
+module PathError
+import FileIO: File, @format_str
+save(file::File{format"PATHERROR"}, data) = nothing
+load(file::File{format"PATHERROR"}) = nothing
+end
+add_format(format"PATHERROR", (), ".patherror", [:PathError])
+
+@testset "Path errors" begin
+    # handling a nonexistent parent directory, during save
+    temp_dir = joinpath(mktempdir(), "dir_that_did_not_exist")
+    @assert !isdir(temp_dir) "Testing error. This dir shouldn't exist"
+    fn = joinpath(temp_dir, "file.patherror")
+    save(fn, "test content")
+    @test isdir(temp_dir)
+    
+    # handling a filepath that's an existing directory, during save
+    @test_throws ArgumentError save(format"PATHERROR", mktempdir(), "test content")
+    
+    # handling a nonexistent filepath, during load
+    @test_throws ArgumentError load(joinpath(mktempdir(), "dummy.patherror"))
+end
+
 @testset "Not installed" begin
     add_format(format"NotInstalled", (), ".not_installed", [:NotInstalled])
     @test_throws ArgumentError save("test.not_installed", nothing)
@@ -60,6 +82,10 @@ end
         [:MultiError1],
         [:MultiError2]
     )
-    ret = @test_throws ErrorException load("test.multierr")
+    tmpfile = joinpath(mktempdir(), "test.multierr")
+    open(tmpfile, "w") do io
+        println(io, "dummy content")
+    end
+    ret = @test_throws ErrorException load(tmpfile)
     #@test ret.value.msg == "1" # this is 0.5 only
 end

test/files/file.csv

@@ -0,0 +1,2 @@
+dummy,data
+0,1