CMake: Add LV2_AUTO_MANIFEST and juce_enable_lv2_manifest_step

docs/CMake API.md

@@ -714,6 +714,15 @@ attributes directly to these creation functions, rather than adding them later.
   `kARAPlaybackTransformationContentBasedFadeAtTail`,
   `kARAPlaybackTransformationContentBasedFadeAtHead`.
 
+`LV2_AUTO_MANIFEST`
+- May be either `TRUE` or `FALSE`. Defaults to `TRUE`. When `TRUE`, a `POST_BUILD` step will be
+  added to the LV2 target which will generate the LV2 turtle manifest files into the plugin bundle
+  directory. This is normally desirable, but does require that the plugin can be successfully
+  loaded immediately after building the LV2 target. If the plugin needs further processing before
+  it can be loaded (e.g. custom signing), then set this option to FALSE to disable the automatic
+  manifest generation. To generate the manifest at a later point in the build, use the
+  `juce_enable_lv2_manifest_step` function.
+
 `VST3_AUTO_MANIFEST`
 - May be either `TRUE` or `FALSE`. Defaults to `TRUE`. When `TRUE`, a `POST_BUILD` step will be
   added to the VST3 target which will generate a `moduleinfo.json` file into the Resources
@@ -798,6 +807,21 @@ bundle) must be executed before the plugin can be loaded. In such cases, you sho
 `VST3_AUTO_MANIFEST FALSE`, use `add_custom_command(TARGET POST_BUILD)` to add your own post-build
 steps, and then finally call `juce_enable_vst3_manifest_step`.
 
+#### `juce_enable_lv2_manifest_step`
+
+    juce_enable_lv2_manifest_step(<target>)
+
+You may call this function to manually enable LV2 manifest generation on a plugin. The argument to
+this function should be a target previously created with `juce_add_plugin`. If that target was
+configured without the LV2 format, this function does nothing, so it is safe to call
+unconditionally in projects that only enable LV2 on some platforms.
+
+`LV2_AUTO_MANIFEST TRUE` will cause the LV2 manifest to be generated immediately after building.
+This is not always appropriate, if extra build steps (such as signing or modifying the plugin
+bundle) must be executed before the plugin can be loaded. In such cases, you should set
+`LV2_AUTO_MANIFEST FALSE`, use `add_custom_command(TARGET POST_BUILD)` to add your own post-build
+steps, and then finally call `juce_enable_lv2_manifest_step`.
+
 #### `juce_set_<kind>_sdk_path`
 
     juce_set_aax_sdk_path(<absolute path>)

extras/Build/CMake/JUCEUtils.cmake

@@ -1170,6 +1170,41 @@ function(juce_enable_vst3_manifest_step shared_code_target)
     set_target_properties(${shared_code_target} PROPERTIES _JUCE_VST3_MANIFEST_STEP_ADDED TRUE)
 endfunction()
 
+function(juce_enable_lv2_manifest_step shared_code_target)
+    get_target_property(manifest_step_added ${shared_code_target} _JUCE_LV2_MANIFEST_STEP_ADDED)
+
+    if(manifest_step_added)
+        message(WARNING "LV2 manifest generation has already been enabled for target ${shared_code_target}. "
+            "You may need to set LV2_AUTO_MANIFEST FALSE in juce_add_plugin, and/or check that you're "
+            "not calling juce_enable_lv2_manifest_step multiple times.")
+        return()
+    endif()
+
+    get_target_property(copy_step_added ${shared_code_target} _JUCE_PLUGIN_COPY_STEP_ADDED)
+
+    if(copy_step_added)
+        message(FATAL_ERROR "LV2 manifest generation would run after plugin copy step, so it has been disabled. "
+            "If you're manually calling juce_enable_lv2_manifest_step, then you probably need to call "
+            "juce_enable_copy_plugin_step too.")
+    endif()
+
+    set(target_name ${shared_code_target}_LV2)
+
+    # Formats that can't be built are quietly dropped from a plugin's FORMATS,
+    # so a plugin configured without an LV2 target is not an error.
+    if(NOT TARGET ${target_name})
+        return()
+    endif()
+
+    _juce_add_lv2_manifest_helper_target()
+
+    add_custom_command(TARGET ${target_name} POST_BUILD
+        COMMAND juce_lv2_helper "$<TARGET_FILE:${target_name}>"
+        VERBATIM)
+
+    set_target_properties(${shared_code_target} PROPERTIES _JUCE_LV2_MANIFEST_STEP_ADDED TRUE)
+endfunction()
+
 # ==================================================================================================
 
 function(_juce_disable_system_includes target)
@@ -1404,11 +1439,11 @@ function(_juce_set_plugin_target_properties shared_code_target kind)
 
         _juce_adhoc_sign(${target_name})
 
-        _juce_add_lv2_manifest_helper_target()
+        get_target_property(lv2_auto_manifest ${shared_code_target} JUCE_LV2_AUTO_MANIFEST)
 
-        add_custom_command(TARGET ${target_name} POST_BUILD
-            COMMAND juce_lv2_helper "$<TARGET_FILE:${target_name}>"
-            VERBATIM)
+        if(lv2_auto_manifest)
+            juce_enable_lv2_manifest_step(${shared_code_target})
+        endif()
 
         _juce_set_copy_properties(${shared_code_target} ${target_name} "${output_path}" JUCE_LV2_COPY_DIR)
     endif()
@@ -1862,6 +1897,7 @@ function(_juce_set_fallback_properties target)
     _juce_set_property_if_not_set(${target} APP_SANDBOX_INHERIT FALSE)
 
     _juce_set_property_if_not_set(${target} VST3_AUTO_MANIFEST TRUE)
+    _juce_set_property_if_not_set(${target} LV2_AUTO_MANIFEST TRUE)
 
     get_target_property(is_synth ${target} JUCE_IS_SYNTH)
 
@@ -2092,6 +2128,7 @@ function(_juce_initialise_target target)
         APP_SANDBOX_ENABLED
         APP_SANDBOX_INHERIT
         VST3_AUTO_MANIFEST
+        LV2_AUTO_MANIFEST
 
         PLUGIN_NAME
         PLUGIN_MANUFACTURER_CODE