feat: have an env variable to control if terminal log has color (#554)

core/include_internal/ten_utils/log/formatter.h

@@ -10,6 +10,13 @@
 
 #include "ten_utils/log/log.h"
 
+typedef void (*ten_log_formatter_func_t)(ten_string_t *buf, TEN_LOG_LEVEL level,
+                                         const char *func_name,
+                                         size_t func_name_len,
+                                         const char *file_name,
+                                         size_t file_name_len, size_t line_no,
+                                         const char *msg, size_t msg_len);
+
 TEN_UTILS_PRIVATE_API void ten_log_default_formatter(
     ten_string_t *buf, TEN_LOG_LEVEL level, const char *func_name,
     size_t func_name_len, const char *file_name, size_t file_name_len,
@@ -22,3 +29,6 @@ TEN_UTILS_PRIVATE_API void ten_log_colored_formatter(
 
 TEN_UTILS_PRIVATE_API void ten_log_set_formatter(
     ten_log_t *self, ten_log_formatter_func_t format_cb, void *user_data);
+
+TEN_UTILS_PRIVATE_API ten_log_formatter_func_t
+ten_log_get_formatter_by_name(const char *name);

core/src/ten_utils/log/formatter.c

@@ -6,6 +6,8 @@
 //
 #include "ten_utils/ten_config.h"
 
+#include "include_internal/ten_utils/log/formatter.h"
+
 #include <inttypes.h>
 #include <time.h>
 
@@ -17,6 +19,33 @@
 #include "ten_utils/lib/string.h"
 #include "ten_utils/log/log.h"
 
+typedef struct ten_log_formatter_entry_t {
+  const char *name;
+  ten_log_formatter_func_t formatter_func;
+} ten_log_formatter_entry_t;
+
+static ten_log_formatter_entry_t registered_formatters[] = {
+    {"default", ten_log_default_formatter},
+    {"color", ten_log_colored_formatter},
+};
+
+static const size_t registered_formatters_size =
+    sizeof(registered_formatters) / sizeof(ten_log_formatter_entry_t);
+
+ten_log_formatter_func_t ten_log_get_formatter_by_name(const char *name) {
+  TEN_ASSERT(name, "Invalid argument.");
+
+  ten_log_formatter_func_t result = NULL;
+
+  for (size_t i = 0; i < registered_formatters_size; i++) {
+    if (strcmp(registered_formatters[i].name, name) == 0) {
+      return registered_formatters[i].formatter_func;
+    }
+  }
+
+  return NULL;
+}
+
 void ten_log_set_formatter(ten_log_t *self, ten_log_formatter_func_t format_cb,
                            void *user_data) {
   TEN_ASSERT(self, "Invalid argument.");

core/src/ten_utils/log/output.c

@@ -250,12 +250,29 @@ void ten_log_output_to_stderr_cb(ten_string_t *msg, void *user_data) {
 void ten_log_set_output_to_stderr(ten_log_t *self) {
   ten_log_output_set(self, ten_log_output_to_stderr_cb, NULL, NULL);
 
+  ten_log_formatter_func_t formatter_func = NULL;
+
 #if defined(OS_LINUX) || defined(OS_MACOS)
-  ten_log_set_formatter(self, ten_log_colored_formatter, NULL);
-  // ten_log_set_formatter(self, ten_log_default_formatter, NULL);
+  formatter_func = ten_log_colored_formatter;
 #else
-  ten_log_set_formatter(self, ten_log_default_formatter, NULL);
+  formatter_func = ten_log_default_formatter;
 #endif
+
+  // The default formatter for `stderr` can be overridden using the below
+  // environment variable.
+  const char *formatter_env = getenv("TEN_LOG_FORMATTER");
+  if (formatter_env) {
+    ten_log_formatter_func_t formatter_func_from_env =
+        ten_log_get_formatter_by_name(formatter_env);
+
+    // If the environment variable specifies a formatter, use it; otherwise,
+    // stick to the default.
+    if (formatter_func_from_env) {
+      formatter_func = formatter_func_from_env;
+    }
+  }
+
+  ten_log_set_formatter(self, formatter_func, NULL);
 }
 
 void ten_log_output_to_file_deinit(ten_log_t *self) {