Mark MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION as requiring html output (#24849)

The code for handling this setting and performing the streaming exists
only in the generated html.

Also error out if MINIMAL_RUNTIME_STREAMING_WASM_* are used without
MINIMAL_RUNTIME.

Author: sbc100

ChangeLog.md

@@ -20,6 +20,9 @@ See docs/process.md for more on how version tagging works.
 
 4.0.13 (in development)
 -----------------------
+- emcc will now error if `MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION` is used
+  when not generating html output.  This was always incompatible but previously
+  ignored. (#24849)
 
 4.0.12 - 08/01/25
 -----------------

site/source/docs/tools_reference/settings_reference.rst

@@ -2954,6 +2954,7 @@ For large .wasm modules and production environments, this should be set to 1
 for faster startup speeds. However this setting is disabled by default
 since it requires server side configuration and for really small pages there
 is no observable difference (also has a ~100 byte impact to code size)
+This setting is only compatible with html output.
 
 Default value: false
 

src/settings.js

@@ -1938,6 +1938,7 @@ var MINIMAL_RUNTIME = 0;
 // for faster startup speeds. However this setting is disabled by default
 // since it requires server side configuration and for really small pages there
 // is no observable difference (also has a ~100 byte impact to code size)
+// This setting is only compatible with html output.
 // [link]
 var MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION = false;
 

test/test_core.py

@@ -8789,16 +8789,13 @@ def test_no_declare_asm_module_exports(self):
   @no_modularize_instance('MODULARIZE=instance is not compatible with MINIMAL_RUNTIME')
   @parameterized({
     'default': ([],),
-    'streaming': (['-sMINIMAL_RUNTIME_STREAMING_WASM_COMPILATION'],),
     'streaming_inst': (['-sMINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION'],),
     'no_export': (['-sDECLARE_ASM_MODULE_EXPORTS=0'],),
   })
   @requires_node  # TODO: Support for non-Node.js shells under MINIMAL_RUNTIME
   def test_minimal_runtime_hello_world(self, args):
-    self.cflags = args
-    self.set_setting('MINIMAL_RUNTIME')
     self.maybe_closure()
-    self.do_runf('small_hello_world.c', 'hello!')
+    self.do_runf('small_hello_world.c', 'hello!', cflags=['-sMINIMAL_RUNTIME'] + args)
 
   # Test that printf() works in MINIMAL_RUNTIME=1
   @no_wasmfs('https://github.com/emscripten-core/emscripten/issues/16816')

test/test_other.py

@@ -1651,6 +1651,16 @@ def test_minimal_runtime_export_all_modularize(self):
     ''')
     self.assertContained('libf1\nlibf2\n', self.run_js('main.mjs'))
 
+  def test_minimal_runtime_errors(self):
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sMINIMAL_RUNTIME_STREAMING_WASM_COMPILATION'])
+    self.assertContained('emcc: error: MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION requires MINIMAL_RUNTIME', err)
+
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sMINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION'])
+    self.assertContained('emcc: error: MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION requires MINIMAL_RUNTIME', err)
+
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sMINIMAL_RUNTIME', '-sMINIMAL_RUNTIME_STREAMING_WASM_COMPILATION'])
+    self.assertContained('emcc: error: MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION is only compatible with html output', err)
+
   def test_export_all_and_exported_functions(self):
     # EXPORT_ALL should not export library functions by default.
     # This means that to export library function you also need to explicitly

tools/link.py

@@ -1057,6 +1057,15 @@ def limit_incoming_module_api():
   if settings.MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION and settings.MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION:
     exit_with_error('MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION and MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION are mutually exclusive!')
 
+  if settings.MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION and not settings.MINIMAL_RUNTIME:
+    exit_with_error('MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION requires MINIMAL_RUNTIME')
+
+  if settings.MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION and not settings.MINIMAL_RUNTIME:
+    exit_with_error('MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION requires MINIMAL_RUNTIME')
+
+  if settings.MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION and options.oformat != OFormat.HTML:
+    exit_with_error('MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION is only compatible with html output')
+
   if options.use_closure_compiler:
     settings.USE_CLOSURE_COMPILER = 1