Use a polyfill to make the JS tests pass

lib/wasi/src/runtime/resolver/filesystem_source.rs

@@ -1,5 +1,4 @@
 use anyhow::{Context, Error};
-use url::Url;
 use webc::compat::Container;
 
 use crate::runtime::resolver::{
@@ -29,8 +28,8 @@ impl Source for FileSystemSource {
         let container = Container::from_disk(&path)
             .with_context(|| format!("Unable to parse \"{}\"", path.display()))?;
 
-        let url = Url::from_file_path(&path)
-            .map_err(|_| anyhow::anyhow!("Unable to turn \"{}\" into a URL", path.display()))?;
+        let url = crate::runtime::resolver::polyfills::url_from_file_path(&path)
+            .ok_or_else(|| anyhow::anyhow!("Unable to turn \"{}\" into a URL", path.display()))?;
 
         let summary = PackageSummary {
             pkg: PackageInfo::from_manifest(container.manifest())?,

lib/wasi/src/runtime/resolver/in_memory_source.rs

@@ -107,7 +107,6 @@ impl Source for InMemorySource {
 #[cfg(test)]
 mod tests {
     use tempfile::TempDir;
-    use url::Url;
 
     use crate::runtime::resolver::{
         inputs::{DistributionInfo, PackageInfo},
@@ -162,7 +161,10 @@ mod tests {
                     entrypoint: None,
                 },
                 dist: DistributionInfo {
-                    webc: Url::from_file_path(bash.canonicalize().unwrap()).unwrap(),
+                    webc: crate::runtime::resolver::polyfills::url_from_file_path(
+                        bash.canonicalize().unwrap()
+                    )
+                    .unwrap(),
                     webc_sha256: [
                         7, 226, 190, 131, 173, 231, 130, 245, 207, 185, 51, 189, 86, 85, 222, 37,
                         27, 163, 170, 27, 25, 24, 211, 136, 186, 233, 174, 119, 66, 15, 134, 9

lib/wasi/src/runtime/resolver/inputs.rs

@@ -134,9 +134,10 @@ impl PackageSummary {
         let path = path.as_ref().canonicalize()?;
         let container = Container::from_disk(&path)?;
         let webc_sha256 = WebcHash::for_file(&path)?;
-        let url = Url::from_file_path(&path).map_err(|_| {
-            anyhow::anyhow!("Unable to turn \"{}\" into a file:// URL", path.display())
-        })?;
+        let url =
+            crate::runtime::resolver::polyfills::url_from_file_path(&path).ok_or_else(|| {
+                anyhow::anyhow!("Unable to turn \"{}\" into a file:// URL", path.display())
+            })?;
 
         let pkg = PackageInfo::from_manifest(container.manifest())?;
         let dist = DistributionInfo {

lib/wasi/src/runtime/resolver/mod.rs

@@ -1,17 +1,18 @@
+mod filesystem_source;
 mod in_memory_source;
 mod inputs;
 mod multi_source_registry;
 mod outputs;
 mod registry;
 mod resolve;
 mod source;
+pub(crate) mod polyfills;
 mod wapm_source;
 mod web_source;
-mod filesystem_source;
 
 pub use self::{
-    in_memory_source::InMemorySource,
     filesystem_source::FileSystemSource,
+    in_memory_source::InMemorySource,
     inputs::{
         Command, Dependency, DistributionInfo, PackageInfo, PackageSpecifier, PackageSummary,
         WebcHash,

lib/wasi/src/runtime/resolver/polyfills.rs

@@ -0,0 +1,50 @@
+use std::path::Path;
+
+use url::Url;
+
+/// Polyfill for [`Url::from_file_path()`] that works on `wasm32-unknown-unknown`.
+pub(crate) fn url_from_file_path(path: impl AsRef<Path>) -> Option<Url> {
+    let path = path.as_ref();
+
+    if !path.is_absolute() {
+        return None;
+    }
+
+    let mut buffer = String::new();
+
+    for component in path {
+        if !buffer.ends_with('/') {
+            buffer.push('/');
+        }
+
+        buffer.push_str(component.to_str()?);
+    }
+
+    buffer.insert_str(0, "file://");
+
+    buffer.parse().ok()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[cfg(unix)]
+    fn behaviour_is_identical() {
+        let inputs = [
+            "/",
+            "/path",
+            "/path/to/file.txt",
+            "./path/to/file.txt",
+            ".",
+            "",
+        ];
+
+        for path in inputs {
+            let got = url_from_file_path(path);
+            let expected = Url::from_file_path(path).ok();
+            assert_eq!(got, expected, "Mismatch for \"{path}\"");
+        }
+    }
+}

lib/wasi/src/state/env.rs

@@ -856,10 +856,14 @@ impl WasiEnv {
     /// Make all the commands in a [`BinaryPackage`] available to the WASI
     /// instance.
     ///
-    /// The [`BinaryPackageCommand::atom()`] will be saved to `/bin/command`.
+    /// The [`BinaryPackageCommand::atom()`][cmd-atom] will be saved to
+    /// `/bin/command`.
     ///
     /// This will also merge the command's filesystem
-    /// ([`BinaryPackage::webc_fs`]) into the current filesystem.
+    /// ([`BinaryPackage::webc_fs`][pkg-fs]) into the current filesystem.
+    ///
+    /// [cmd-atom]: crate::bin_factory::BinaryPackageCommand::atom()
+    /// [pkg-fs]: crate::bin_factory::BinaryPackage::webc_fs
     pub fn use_package(&self, pkg: &BinaryPackage) -> Result<(), WasiStateCreationError> {
         // PERF: We should avoid all these copies in the WasiFsRoot::Backing case.