`StepOptions.preload_paths` does not allow directories as input

[miker2049]

According to emscripten docs, --embed-file and --preload-file accept directory inputs, which will bundle everything in the directory into the js/.data file accordingly. Currently, an input with options like so will error:

        const opts: StepOptions = .{
            .optimize = optimize,
            .flags = emcc_flags,
            .settings = emcc_settings,
            .install_dir = install_dir,
            .out_file_name = "main.html",
            .preload_paths = &.{.{ .src_path = b.path("assets/") }},  // <--- here
        };

Relevant error:

...
run
└─ run dependency
   └─ install generated/
      └─ run dependency (main.html) failure
error: failed checking cache: /home/user/project/assets file_hash IsDir

Build Summary: 19/23 steps succeeded (1 failed)
run transitive failure
└─ run dependency transitive failure
   └─ install generated/ transitive failure
      ├─ run dependency (main.html) failure
      └─ run dependency (main.html) (+3 more reused dependencies)
...

Here is a hacky fix, the clear issue is .addFileArg deals with the cache and expects a file input. So, simply passing string of the path as the arg fixes the problem :

diff --git a/build.zig b/build.zig
index b16f992..3a06129 100644
--- a/build.zig
+++ b/build.zig
@@ -247,7 +247,7 @@ pub fn emccStep(
     if (options.preload_paths) |preload_paths| {
         for (preload_paths) |path| {
             emcc.addArg("--preload-file");
-            emcc.addFileArg(path.src_path);
+            emcc.addArg(path.src_path.getDisplayName());
         }
     }

There is probably better solution here.. getDisplayName for one is deprecated apparently.

[miker2049]

Given the ResourceFile interface here, the correct fix I believe should be:

diff --git a/build.zig b/build.zig
index b16f992..3a06129 100644
--- a/build.zig
+++ b/build.zig
@@ -247,7 +247,7 @@ pub fn emccStep(
     if (options.preload_paths) |preload_paths| {
         for (preload_paths) |path| {
             emcc.addArg("--preload-file");
-            emcc.addFileArg(path.src_path);
+            emcc.addArg(path.get(b));
         }
     }