pass more --dirs to wasmtime so it can read the entire module tree

This allows compress/flate to pass on -target=wasi out of the box

Fixes #2367

builder/build.go

@@ -45,6 +45,11 @@ type BuildResult struct {
 	// binary must be run in the directory of the tested package.
 	MainDir string
 
+	// The root of the Go module tree.  This is used for running tests in emulator
+	// that restrict file system access to allow them to grant access to the entire
+	// source tree they're likely to need to read testdata from.
+	ModuleRoot string
+
 	// ImportPath is the import path of the main package. This is useful for
 	// correctly printing test results: the import path isn't always the same as
 	// the path listed on the command line.
@@ -799,9 +804,18 @@ func Build(pkgName, outpath string, config *compileopts.Config, action func(Buil
 	default:
 		return fmt.Errorf("unknown output binary format: %s", outputBinaryFormat)
 	}
+
+	// If there's a module root, use that.
+	moduleroot := lprogram.MainPkg().Module.Dir
+	if moduleroot == "" {
+		// if not, just the regular root
+		moduleroot = lprogram.MainPkg().Root
+	}
+
 	return action(BuildResult{
 		Binary:     tmppath,
 		MainDir:    lprogram.MainPkg().Dir,
+		ModuleRoot: moduleroot,
 		ImportPath: lprogram.MainPkg().ImportPath,
 	})
 }

loader/loader.go

@@ -47,6 +47,14 @@ type PackageJSON struct {
 	ImportPath string
 	Name       string
 	ForTest    string
+	Root       string
+	Module     struct {
+		Path      string
+		Main      bool
+		Dir       string
+		GoMod     string
+		GoVersion string
+	}
 
 	// Source files
 	GoFiles  []string

main.go

@@ -233,6 +233,19 @@ func Test(pkgName string, stdout, stderr io.Writer, options *compileopts.Options
 	return passed, err
 }
 
+func dirsToModuleRoot(maindir, modroot string) []string {
+	var dirs = []string{"."}
+	last := ".."
+	// strip off path elements until we hit the module root
+	// adding `..`, `../..`, `../../..` until we're done
+	for maindir != modroot {
+		dirs = append(dirs, last)
+		last = filepath.Join(last, "..")
+		maindir = filepath.Dir(maindir)
+	}
+	return dirs
+}
+
 // runPackageTest runs a test binary that was previously built. The return
 // values are whether the test passed and any errors encountered while trying to
 // run the binary.
@@ -269,9 +282,12 @@ func runPackageTest(config *compileopts.Config, stdout, stderr io.Writer, result
 			args = append(args, "--dir="+tmpdir, "--env=TMPDIR="+tmpdir)
 			// TODO: add option to not delete temp dir for debugging?
 			defer os.RemoveAll(tmpdir)
-			// allow reading from current directory: --dir=.
+			// allow reading from directories up to module root
+			for _, d := range dirsToModuleRoot(result.MainDir, result.ModuleRoot) {
+				args = append(args, "--dir="+d)
+			}
 			// mark end of wasmtime arguments and start of program ones: --
-			args = append(args, "--dir=.", "--")
+			args = append(args, "--")
 			if testVerbose {
 				args = append(args, "-test.v")
 			}