Support include empty config file. v5.0.173 v6.0.68 (#3768)

SRS supports including another configuration in the include package.
When generating configurations, we can only generate the changed
configurations, while the unchanged configurations are in the fixed
files, for example:

```nginx
listen 1935;
include server.conf;
```

In `server.conf`, we can manage the changing configurations with the
program:

```nginx
http_api { enabled on; }
```

However, during system initialization, we often create an empty
`server.conf`, and the content is generated only after the program
starts, so `server.conf` might be an empty file. This also makes it
convenient to use a script to confirm the existence of this file:

```bash
touch server.conf
```

Currently, SRS does not support empty configurations and will report an
error. This PR is to solve this problem, making it more convenient to
use include.

`TRANS_BY_GPT4`

---------

Co-authored-by: Haibo Chen <495810242@qq.com>

trunk/src/utest/srs_utest_config.cpp

@@ -85,11 +85,14 @@ srs_error_t MockSrsConfig::build_buffer(std::string src, srs_internal::SrsConfig
 {
     srs_error_t err = srs_success;
 
-    string content = included_files[src];
-    if(content.empty()) {
+    // No file, error.
+    if(included_files.find(src) == included_files.end()) {
         return srs_error_new(ERROR_SYSTEM_CONFIG_INVALID, "file %s: no found", src.c_str());
     }
 
+    string content = included_files[src];
+
+    // Empty file, ok.
     *pbuffer = new MockSrsConfigBuffer(content);
 
     return err;
@@ -689,10 +692,30 @@ VOID TEST(ConfigDirectiveTest, ParseInvalidNoEndOfDirective)
 VOID TEST(ConfigDirectiveTest, ParseInvalidNoEndOfSubDirective)
 {
     srs_error_t err;
-    
-    MockSrsConfigBuffer buf("dir0 {");
-    SrsConfDirective conf;
-    HELPER_ASSERT_FAILED(conf.parse(&buf));
+
+    if (true) {
+        MockSrsConfigBuffer buf("");
+        SrsConfDirective conf;
+        HELPER_ASSERT_SUCCESS(conf.parse(&buf));
+    }
+
+    if (true) {
+        MockSrsConfigBuffer buf("# OK");
+        SrsConfDirective conf;
+        HELPER_ASSERT_SUCCESS(conf.parse(&buf));
+    }
+
+    if (true) {
+        MockSrsConfigBuffer buf("dir0 {");
+        SrsConfDirective conf;
+        HELPER_ASSERT_FAILED(conf.parse(&buf));
+    }
+
+    if (true) {
+        MockSrsConfigBuffer buf("dir0 {} dir1 {");
+        SrsConfDirective conf;
+        HELPER_ASSERT_FAILED(conf.parse(&buf));
+    }
 }
 
 VOID TEST(ConfigDirectiveTest, ParseInvalidNoStartOfSubDirective)

trunk/src/utest/srs_utest_config2.cpp

@@ -0,0 +1,47 @@
+//
+// Copyright (c) 2013-2023 The SRS Authors
+//
+// SPDX-License-Identifier: MIT or MulanPSL-2.0
+//
+#include <srs_utest_config2.hpp>
+
+#include <srs_kernel_error.hpp>
+#include <srs_kernel_file.hpp>
+#include <srs_utest_kernel.hpp>
+
+VOID TEST(ConfigMainTest, CheckIncludeEmptyConfig)
+{
+    srs_error_t err;
+
+    if (true) {
+        string filepath = _srs_tmp_file_prefix + "utest-main.conf";
+        MockFileRemover _mfr(filepath);
+
+        string included = _srs_tmp_file_prefix + "utest-included-empty.conf";
+        MockFileRemover _mfr2(included);
+
+        if (true) {
+            SrsFileWriter fw;
+            fw.open(included);
+        }
+
+        if (true) {
+            SrsFileWriter fw;
+            fw.open(filepath);
+            string content = _MIN_OK_CONF "include " + included + ";";
+            fw.write((void*)content.data(), (int)content.length(), NULL);
+        }
+
+        SrsConfig conf;
+        HELPER_ASSERT_SUCCESS(conf.parse_file(filepath.c_str()));
+        EXPECT_EQ(1, (int)conf.get_listens().size());
+    }
+
+    if (true) {
+        MockSrsConfig conf;
+        conf.mock_include("test.conf", "");
+        HELPER_ASSERT_SUCCESS(conf.parse(_MIN_OK_CONF "include test.conf;"));
+        EXPECT_EQ(1, (int)conf.get_listens().size());
+    }
+}
+

trunk/src/utest/srs_utest_config2.hpp

@@ -0,0 +1,16 @@
+//
+// Copyright (c) 2013-2023 The SRS Authors
+//
+// SPDX-License-Identifier: MIT or MulanPSL-2.0
+//
+
+#ifndef SRS_UTEST_CONFIG2_HPP
+#define SRS_UTEST_CONFIG2_HPP
+
+/*
+#include <srs_utest_config2.hpp>
+*/
+#include <srs_utest_config.hpp>
+
+#endif
+