[component_manager] Implement fuchsia-boot

TEST=fx run-test-component component_manager_tests

CF-536 #comment

"Despite its stocky shape and short legs, it can easily outrun most
humans. Hippos have been clocked at 30 km/h over short distances"

Change-Id: I157e83298f2437982068c272c08527bb6ab7c570

garnet/bin/sys/component_manager/BUILD.gn

@@ -72,6 +72,13 @@ test_package("component_manager_tests") {
     },
   ]
 
+  meta = [
+    {
+      path = rebase_path("meta/component_manager_tests_hello_world.cml")
+      dest = "component_manager_tests_hello_world.cm"
+    },
+  ]
+
   binaries = [
     {
       name = "hello_world"

garnet/bin/sys/component_manager/meta/component_manager_tests_hello_world.cml

+{
+    "program": {
+        "binary": "bin/hello_world"
+    }
+}

garnet/bin/sys/component_manager/src/fuchsia_boot_resolver.rs

@@ -3,10 +3,14 @@
 // found in the LICENSE file.
 
 use {
+    crate::io_util,
     crate::model::{Resolver, ResolverError},
-    failure::format_err,
-    fidl_fuchsia_data as fdata, fidl_fuchsia_sys2 as fsys,
+    cm_fidl_translator::translate,
+    fidl::endpoints::ClientEnd,
+    fidl_fuchsia_sys2 as fsys,
+    fuchsia_uri::boot_uri::FuchsiaBootUri,
     futures::future::FutureObj,
+    std::path::PathBuf,
 };
 
 pub static SCHEME: &str = "fuchsia-boot";
@@ -14,7 +18,7 @@ pub static SCHEME: &str = "fuchsia-boot";
 /// Resolves component URIs with the "fuchsia-boot" scheme.
 ///
 /// URI syntax:
-/// - fuchsia-boot:///path/to/directory#meta/component.cm
+/// - fuchsia-boot:///directory#meta/component.cm
 pub struct FuchsiaBootResolver {}
 
 impl FuchsiaBootResolver {
@@ -26,32 +30,36 @@ impl FuchsiaBootResolver {
         &'a self,
         component_uri: &'a str,
     ) -> Result<fsys::Component, ResolverError> {
-        // TODO: Actually resolve and parse CM files from the boot filesystem.
-        println!("FuchsiaBootResolver: pretending to resolve '{}'", component_uri);
-        if component_uri == "fuchsia-boot:///boot#meta/scaffold.cm" {
-            Ok(fsys::Component {
-                resolved_uri: Some(component_uri.to_string()),
-                decl: Some(fsys::ComponentDecl {
-                    program: Some(fdata::Dictionary {
-                        entries: vec![fdata::Entry {
-                            key: "binary".to_string(),
-                            value: Some(Box::new(fdata::Value::Str("bin/scaffold".to_string()))),
-                        }],
-                    }),
-                    uses: None,
-                    exposes: None,
-                    offers: None,
-                    facets: None,
-                    children: None,
-                }),
-                package: None,
-            })
-        } else {
-            Err(ResolverError::component_not_available(
-                component_uri,
-                format_err!("unknown component"),
-            ))
-        }
+        // Parse URI.
+        let uri = FuchsiaBootUri::parse(component_uri)
+            .map_err(|e| ResolverError::component_not_available(component_uri, e))?;
+        let res = uri.resource().ok_or(ResolverError::uri_missing_resource_error(component_uri))?;
+        let res_path = PathBuf::from(uri.path()).join(PathBuf::from(res));
+        let res_path_str =
+            res_path.to_str().ok_or(ResolverError::uri_missing_resource_error(component_uri))?;
+
+        // Read component manifest from resource into a component decl.
+        let cm_file = await!(io_util::open_file_in_namespace(&res_path_str))
+            .map_err(|e| ResolverError::component_not_available(component_uri, e))?;
+        let cm_str = await!(io_util::read_file(&cm_file))
+            .map_err(|e| ResolverError::component_not_available(component_uri, e))?;
+        let component_decl = translate(&cm_str)
+            .map_err(|e| ResolverError::component_not_available(component_uri, e))?;
+
+        // Set up the fuchsia-boot path as the component's "package" namespace.
+        let package_path = uri.path();
+        let path_proxy = await!(io_util::open_directory_in_namespace(&package_path))
+            .map_err(|e| ResolverError::component_not_available(component_uri, e))?;
+        let package = fsys::Package {
+            package_uri: Some(uri.root_uri().to_string()),
+            package_dir: Some(ClientEnd::new(path_proxy.into_channel().unwrap().into_zx_channel())),
+        };
+
+        Ok(fsys::Component {
+            resolved_uri: Some(component_uri.to_string()),
+            decl: Some(component_decl),
+            package: Some(package),
+        })
     }
 }
 
@@ -63,3 +71,23 @@ impl Resolver for FuchsiaBootResolver {
         FutureObj::new(Box::new(self.resolve_async(component_uri)))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use {super::*, fuchsia_async as fasync};
+
+    #[test]
+    fn hello_world_test() {
+        let mut executor = fasync::Executor::new().unwrap();
+        executor.run_singlethreaded(
+            async {
+                let resolver = FuchsiaBootResolver::new();
+                let component = await!(resolver.resolve_async(
+                    "fuchsia-boot:///pkg#meta/component_manager_tests_hello_world.cm"
+                ))
+                .unwrap();
+                assert_eq!("fuchsia-boot:///pkg", component.package.unwrap().package_uri.unwrap());
+            },
+        );
+    }
+}