Added warning message when trying to set init-only params per #808 (#816)

src/worker-script/index.js

@@ -172,6 +172,22 @@ res) => {
 };
 
 const setParameters = async ({ payload: { params: _params } }, res) => {
+  // A small number of parameters can only be set at initialization.
+  // These can only be set using (1) the `oem` argument of `initialize` (for setting the oem)
+  // or (2) the `config` argument of `initialize` (for all other settings).
+  // Attempting to set these using this function will have no impact so a warning is printed.
+  // This list is generated by searching the Tesseract codebase for parameters
+  // defined with `[type]_INIT_MEMBER` rather than `[type]_MEMBER`.
+  const initParamNames = ['ambigs_debug_level', 'user_words_suffix', 'user_patterns_suffix', 'user_patterns_suffix',
+    'load_system_dawg', 'load_freq_dawg', 'load_unambig_dawg', 'load_punc_dawg', 'load_number_dawg', 'load_bigram_dawg',
+    'tessedit_ocr_engine_mode', 'tessedit_init_config_only', 'language_model_ngram_on', 'language_model_use_sigmoidal_certainty'];
+
+  const initParamStr = Object.keys(_params)
+    .filter((k) => initParamNames.includes(k))
+    .join(', ');
+
+  if (initParamStr.length > 0) console.log(`Attempted to set parameters that can only be set during initialization: ${initParamStr}`);
+
   Object.keys(_params)
     .filter((k) => !k.startsWith('tessjs_'))
     .forEach((key) => {