Added option to read config file from stdin (related #105)

docs/configuration_file.md

@@ -5,6 +5,7 @@
 * [Top level options](#top-level-options)
   * [Diagram options](#diagram-options)
 * [Example complete config](#example-complete-config)
+* [Determining config file location](#determining-config-file-location)
 * [Paths](#paths)
 
 <!-- tocstop -->
@@ -121,6 +122,18 @@ diagrams:
         - 'title clang-uml class diagram model'
 ```
 
+## Determining config file location
+
+If `-c,--config` option is not provided, `clang-uml` will try to open file
+`.clang-uml` in the current directory and fail if it doesn't exist.
+
+With `-c,--config` option pointing to a valid `.clang-uml` file path, the file
+configuration will be loaded from that file.
+
+Furthermore, when the value of `-c,--config` option is `-` - the entire config
+will be read from `stdin`, which can be useful for scripting and generating
+config Yaml documents on the fly.
+
 ## Paths
 By default, all paths specified in the configuration file, including:
 

src/config/yaml_decoders.cc

@@ -609,14 +609,32 @@ config load(
     const std::string &config_file, std::optional<bool> paths_relative_to_pwd)
 {
     try {
-        YAML::Node doc = YAML::LoadFile(config_file);
+        YAML::Node doc;
+        std::filesystem::path config_file_path{};
+
+        if (config_file == "-") {
+            std::istreambuf_iterator<char> stdin_stream_begin{std::cin};
+            std::istreambuf_iterator<char> stdin_stream_end{};
+            std::string stdin_stream_str{stdin_stream_begin, stdin_stream_end};
+
+            doc = YAML::Load(stdin_stream_str);
+        }
+        else {
+            doc = YAML::LoadFile(config_file);
+        }
 
         // Store the parent path of the config_file to properly resolve
         // the include files paths
-        auto config_file_path =
-            std::filesystem::absolute(std::filesystem::path{config_file});
-        doc.force_insert(
-            "__parent_path", config_file_path.parent_path().string());
+        if (config_file == "-") {
+            config_file_path = std::filesystem::current_path();
+            doc.force_insert("__parent_path", config_file_path.string());
+        }
+        else {
+            config_file_path =
+                std::filesystem::absolute(std::filesystem::path{config_file});
+            doc.force_insert(
+                "__parent_path", config_file_path.parent_path().string());
+        }
 
         //
         // If no relative_to path is specified in the config, make all paths

src/main.cc

@@ -162,9 +162,9 @@ int main(int argc, const char *argv[])
     std::optional<std::string> compilation_database_dir{};
     std::vector<std::string> diagram_names{};
     std::optional<std::string> output_directory{};
-    unsigned int thread_count{0};
+    unsigned int thread_count{};
     bool show_version{false};
-    int verbose{0};
+    int verbose{};
     bool list_diagrams{false};
     bool quiet{false};
     bool initialize{false};
@@ -175,8 +175,8 @@ int main(int argc, const char *argv[])
     bool dump_config{false};
     std::optional<bool> paths_relative_to_pwd{};
 
-    app.add_option(
-        "-c,--config", config_path, "Location of configuration file");
+    app.add_option("-c,--config", config_path,
+        "Location of configuration file, when '-' read from stdin");
     app.add_option("-d,--compile-database", compilation_database_dir,
         "Location of compilation database directory");
     app.add_option("-n,--diagram-name", diagram_names,
@@ -208,42 +208,60 @@ int main(int argc, const char *argv[])
 
     CLI11_PARSE(app, argc, argv);
 
+    if (quiet || dump_config)
+        verbose = 0;
+    else
+        verbose++;
+
+    clanguml::util::setup_logging(verbose);
+
     if (show_version) {
         print_version();
         return 0;
     }
 
+    if ((config_path == "-") &&
+        (initialize || add_class_diagram.has_value() ||
+            add_sequence_diagram.has_value() ||
+            add_package_diagram.has_value() ||
+            add_include_diagram.has_value())) {
+
+        LOG_ERROR(
+            "ERROR: Cannot add a diagram config to configuration from stdin");
+
+        return 1;
+    }
+
     if (initialize) {
         return create_config_file();
     }
 
-    verbose++;
+    if (config_path != "-") {
+        if (add_class_diagram) {
+            return add_config_diagram(
+                clanguml::common::model::diagram_t::kClass, config_path,
+                *add_class_diagram);
+        }
 
-    if (quiet)
-        verbose = 0;
+        if (add_sequence_diagram) {
+            return add_config_diagram(
+                clanguml::common::model::diagram_t::kSequence, config_path,
+                *add_sequence_diagram);
+        }
 
-    if (add_class_diagram) {
-        return add_config_diagram(clanguml::common::model::diagram_t::kClass,
-            config_path, *add_class_diagram);
+        if (add_package_diagram) {
+            return add_config_diagram(
+                clanguml::common::model::diagram_t::kPackage, config_path,
+                *add_package_diagram);
+        }
+
+        if (add_include_diagram) {
+            return add_config_diagram(
+                clanguml::common::model::diagram_t::kInclude, config_path,
+                *add_include_diagram);
+        }
     }
 
-    if (add_sequence_diagram) {
-        return add_config_diagram(clanguml::common::model::diagram_t::kSequence,
-            config_path, *add_sequence_diagram);
-    }
-
-    if (add_package_diagram) {
-        return add_config_diagram(clanguml::common::model::diagram_t::kPackage,
-            config_path, *add_package_diagram);
-    }
-
-    if (add_include_diagram) {
-        return add_config_diagram(clanguml::common::model::diagram_t::kInclude,
-            config_path, *add_include_diagram);
-    }
-
-    clanguml::util::setup_logging(verbose);
-
     clanguml::config::config config;
     try {
         config = clanguml::config::load(config_path, paths_relative_to_pwd);