cmake: add component dependency graph generation helpers

These optional feature produces a graphviz file showing component
dependencies. It is useful for debugging reasons why certain
components got added to the build.

Kconfig

@@ -22,6 +22,11 @@ mainmenu "Espressif IoT Development Framework Configuration"
         bool
         default "n"
 
+    config IDF_TARGET_ARCH
+        string
+        default "riscv" if IDF_TARGET_ARCH_RISCV
+        default "xtensa" if IDF_TARGET_ARCH_XTENSA
+
     config IDF_TARGET
         # This option records the IDF target when sdkconfig is generated the first time.
         # It is not updated if environment variable $IDF_TARGET changes later, and

tools/cmake/build.cmake

@@ -221,13 +221,16 @@ function(__build_expand_requirements component_target)
 
     get_property(reqs TARGET ${component_target} PROPERTY REQUIRES)
     get_property(priv_reqs TARGET ${component_target} PROPERTY PRIV_REQUIRES)
+    __component_get_property(component_name ${component_target} COMPONENT_NAME)
 
     foreach(req ${reqs})
+        depgraph_add_edge(${component_name} ${req} REQUIRES)
         __build_resolve_and_add_req(_component_target ${component_target} ${req} __REQUIRES)
         __build_expand_requirements(${_component_target})
     endforeach()
 
     foreach(req ${priv_reqs})
+        depgraph_add_edge(${component_name} ${req} PRIV_REQUIRES)
         __build_resolve_and_add_req(_component_target ${component_target} ${req} __PRIV_REQUIRES)
         __build_expand_requirements(${_component_target})
     endforeach()

tools/cmake/component_deps.dot.in

@@ -0,0 +1,30 @@
+digraph G {
+
+${depgraph}
+
+subgraph cluster_g0 {
+    rank = same;
+    label = "G0";
+
+    soc;
+    hal;
+    esp_common;
+    esp_rom;
+    ${CONFIG_IDF_TARGET_ARCH};
+    ${CONFIG_IDF_TARGET};
+}
+
+subgraph cluster_g1 {
+    rank = same;
+    label = "G1";
+
+    spi_flash;
+    freertos;
+    log;
+    heap;
+    newlib;
+    esp_system;
+    esp_hw_support;
+}
+
+}

tools/cmake/depgraph.cmake

@@ -0,0 +1,61 @@
+# Component dependency graph generation helpers.
+# To enable this functionality, add:
+#   idf_build_set_property(__BUILD_COMPONENT_DEPGRAPH_ENABLED 1)
+# in the project CMakeLists.txt file between include(project.cmake) and project(name) calls.
+#
+# Graphviz file component_deps.dot will be produced in the build directory.
+# To change the template, see component_deps.dot.in.
+
+# depgraph_add_edge
+#
+# @brief Record an edge in the component dependency graph (dependent -> dependency)
+#
+# @param[in] dep_from dependent name
+# @param[in] dep_to dependency name
+# @param[in, optional] REQUIRES if given, record this as "REQUIRES" (public/interface) dependency
+# @param[in, optional] PRIV_REQUIRES if given, record this as "PRIV_REQUIRES" (private) dependency
+#
+function(depgraph_add_edge dep_from dep_to)
+    cmake_parse_arguments(_ "REQUIRES;PRIV_REQUIRES" "" "" ${ARGN})
+    idf_build_get_property(depgraph_enabled __BUILD_COMPONENT_DEPGRAPH_ENABLED)
+    if(NOT depgraph_enabled)
+        return()
+    endif()
+    idf_build_get_property(common_reqs __COMPONENT_REQUIRES_COMMON)
+
+    set(attr)
+    if(__REQUIRES)
+        set(attr "[class=\"requires\"]")
+    elseif(__PRIV_REQUIRES)
+        set(attr "[class=\"priv_requires\" style=\"dotted\"]")
+    endif()
+
+    if(dep_to IN_LIST common_reqs)
+        # Don't record graph edges leading to "common" components, since every component has these dependencies.
+        # However, show which components are "common" by adding an edge from a node named "common".
+        # If necessary, add a new build property to customize this behavior.
+        if(NOT dep_from IN_LIST common_reqs)
+            idf_build_set_property(__BUILD_COMPONENT_DEPGRAPH "common -> ${dep_to}" APPEND)
+        endif()
+    else()
+        idf_build_set_property(__BUILD_COMPONENT_DEPGRAPH "${dep_from} -> ${dep_to} ${attr}" APPEND)
+    endif()
+endfunction()
+
+# depgraph_generate
+#
+# @brief Write the collected component dependency graph to a file. The file is in Graphviz (.dot) format.
+#
+# @param[in] out_path  name of the output file
+#
+function(depgraph_generate out_path)
+    idf_build_get_property(depgraph_enabled __BUILD_COMPONENT_DEPGRAPH_ENABLED)
+    if(NOT depgraph_enabled)
+        return()
+    endif()
+    idf_build_get_property(depgraph __BUILD_COMPONENT_DEPGRAPH)
+    list(REMOVE_DUPLICATES depgraph)
+    string(REPLACE ";" ";\n" depgraph "${depgraph}")
+    configure_file("${IDF_PATH}/tools/cmake/component_deps.dot.in"
+        "${out_path}")
+endfunction()

tools/cmake/idf.cmake

@@ -41,6 +41,7 @@ if(NOT __idf_env_set)
     include(kconfig)
     include(component)
     include(utilities)
+    include(depgraph)
     include(targets)
     include(ldgen)
     include(dfu)

tools/cmake/project.cmake

@@ -120,6 +120,9 @@ function(__project_info test_components)
     configure_file("${idf_path}/tools/cmake/project_description.json.in"
         "${build_dir}/project_description.json")
 
+    # Generate component dependency graph
+    depgraph_generate("${build_dir}/component_deps.dot")
+
     # We now have the following component-related variables:
     #
     # build_components is the list of components to include in the build.