The mapdir option unexpectedly maps to the current working directory

[caspervonb]

Describe the bug

Take the following rename(2) test from the wasi-test project.

// { "preopens": { "/scratch": "scratch" } }

#include <assert.h>
#include <stdio.h>

int main(void) {
	char oldname[] = "/scratch/oldfile";
	char newname[] = "/scratch/newfile";

	FILE *oldfile = fopen(oldname, "w");
	assert(oldfile != NULL);
	assert(fclose(oldfile) == 0);

	assert(rename(oldname, newname) == 0);

	FILE *newfile = fopen(newname, "r");
	assert(newfile != NULL);
	assert(fclose(newfile) == 0);

	return 0;
}

Which gets invoked as the following command

 wasmer run --mapdir=/scratch:scratch integration/rename.wasm 

echo "`wasmer -V` | `rustc -V` | `uname -m`"
wasmer 0.16.2 | rustc 1.43.1 (8d69840ab 2020-05-04) | x86_64

Steps to reproduce

1. git clone https://github.com/caspervonb/wasi-test
2. python3 build.py
3. wasmer run --mapdir=/scratch:scratch integration/rename.wasm
4. mkdir scratch
5. ls scratch

Expected behavior

/scratch to be mapped to ./scratch and it to contain a single file

Actual behavior

/scratch is mapped to . which contains the created file

Additional context

[syrusakbary]

Thanks for the report @caspervonb !

[MarkMcCaskey]

On wasmer on master I can confirm that wasmer run --mapdir=/scratch:scratch integration/rename.wasm does not work but wasmer run --mapdir=scratch:scratch integration/rename.wasm and wasmer run --mapdir=./scratch:scratch integration/rename.wasm seem to.

I'll look into it some more.

Also the actual commands I've been running look like wasmer run --mapdir=./fixtures:fixtures target/wasm32-wasi/debug/std_fs_rename.wasm