Bug 300382 – [WPE] Build regression after libsoup2 removal breaks third-party pkg-config discovery

• Component: WPE WebKit
• Status: RESOLVED FIXED

[Pablo Saavedra]

**Description:**
A recent commit that removed libsoup2 support has caused a build regression that prevents third-party applications from building against WPEWebKit using `pkg-config`.

Commit is:
```
Author: Adrian Perez de Castro <[e-mail]>
Date:   Tue Oct 7 07:18:51 2025 -0700

[GTK] Remove support for building against libsoup2
https://bugs.webkit.org/show_bug.cgi?id=300163

Canonical link: https://commits.webkit.org/301131@main
```

This change removed the definition of the `SOUP_API_VERSION` variable from the CMake build system, as seen in this diff:

```diff
--- a/Source/cmake/OptionsWPE.cmake
+++ b/Source/cmake/OptionsWPE.cmake
@@ -165,25 +166,14 @@
 endif ()
 
 if (ENABLE_WPE_1_1_API)
-    set(SOUP_MINIMUM_VERSION 3.0.0)
-    set(SOUP_API_VERSION 3.0)
     set(WPE_API_VERSION 1.1)
     set(WPE_API_MAJOR_VERSION 1)
-    set(ENABLE_SERVER_PRECONNECT ON)
     SET_AND_EXPOSE_TO_BUILD(ENABLE_2022_GLIB_API OFF)
 else ()
-    set(SOUP_MINIMUM_VERSION 3.0.0)
-    set(SOUP_API_VERSION 3.0)
     set(WPE_API_VERSION 2.0)
     set(WPE_API_MAJOR_VERSION 2)
-    set(ENABLE_SERVER_PRECONNECT ON)
     SET_AND_EXPOSE_TO_BUILD(ENABLE_2022_GLIB_API ON)
 endif ()
-find_package(LibSoup ${SOUP_MINIMUM_VERSION} REQUIRED)
-
-if (NOT LibSoup_FOUND)
-    message(FATAL_ERROR "libsoup 3 is required.")
-endif ()
```

However, multiple `pkg-config` (`.pc.in`) and TOML (`.toml.in`) template files were not updated and still reference the now-undefined `@SOUP_API_VERSION@` variable. This results in malformed `.pc` files being generated.

```
Source/WebKit/gtk/gtk3-webkitgtk.toml.in:dependencies = ["GObject-2.0", "Gio-2.0", "Gtk-@GTK_API_VERSION@.0", "Soup-@SOUP_API_VERSION@"]
Source/WebKit/gtk/gtk3-webkitgtk.toml.in:[dependencies."Soup-@SOUP_API_VERSION@"]
Source/WebKit/gtk/gtk3-webkitgtk.toml.in:docs_url = "https://gnome.pages.gitlab.gnome.org/libsoup/libsoup-@SOUP_API_VERSION@"
Source/WebKit/gtk/webkitgtk-web-process-extension.pc.in:Requires: glib-2.0 @GTK_PC_NAME@ libsoup-@SOUP_API_VERSION@ javascriptcoregtk-@WEBKITGTK_API_VERSION@
Source/WebKit/gtk/webkitgtk-web-process-extension.toml.in:dependencies = ["GObject-2.0", "Gio-2.0", "Soup-@SOUP_API_VERSION@"]
Source/WebKit/gtk/webkitgtk-web-process-extension.toml.in:[dependencies."Soup-@SOUP_API_VERSION@"]
Source/WebKit/gtk/webkitgtk-web-process-extension.toml.in:docs_url = "https://gnome.pages.gitlab.gnome.org/libsoup/libsoup-@SOUP_API_VERSION@"
Source/WebKit/gtk/webkitgtk.pc.in:Requires: glib-2.0 @GTK_PC_NAME@ libsoup-@SOUP_API_VERSION@ javascriptcoregtk-@WEBKITGTK_API_VERSION@
Source/WebKit/gtk/gtk4-webkitgtk.toml.in:dependencies = ["GObject-2.0", "Gio-2.0", "Gtk-@GTK_API_VERSION@.0", "Soup-@SOUP_API_VERSION@"]
Source/WebKit/gtk/gtk4-webkitgtk.toml.in:[dependencies."Soup-@SOUP_API_VERSION@"]
Source/WebKit/gtk/gtk4-webkitgtk.toml.in:docs_url = "https://gnome.pages.gitlab.gnome.org/libsoup/libsoup-@SOUP_API_VERSION@"
Source/WebKit/wpe/wpewebkit.toml.in:dependencies = ["GObject-2.0", "Gio-2.0", "Soup-@SOUP_API_VERSION@"]
Source/WebKit/wpe/wpewebkit.toml.in:[dependencies."Soup-@SOUP_API_VERSION@"]
Source/WebKit/wpe/wpewebkit.toml.in:docs_url = "https://gnome.pages.gitlab.gnome.org/libsoup/libsoup-@SOUP_API_VERSION@"
Source/WebKit/wpe/wpe-web-process-extension.pc.in:Requires: glib-2.0 libsoup-@SOUP_API_VERSION@ wpe-1.0
Source/WebKit/wpe/wpe-webkit-uninstalled.pc.in:Requires: glib-2.0 libsoup-@SOUP_API_VERSION@ wpe-1.0 @WPE_PLATFORM_PC_UNINSTALLED_REQUIRES@
Source/WebKit/wpe/wpe-web-process-extension.toml.in:dependencies = ["GObject-2.0", "Gio-2.0", "Soup-@SOUP_API_VERSION@"]
Source/WebKit/wpe/wpe-web-process-extension.toml.in:[dependencies."Soup-@SOUP_API_VERSION@"]
Source/WebKit/wpe/wpe-web-process-extension.toml.in:docs_url = "https://gnome.pages.gitlab.gnome.org/libsoup/libsoup-@SOUP_API_VERSION@"
Source/WebKit/wpe/wpe-webkit.pc.in:Requires: glib-2.0 libsoup-@SOUP_API_VERSION@ wpe-1.0 @WPE_PLATFORM_PC_REQUIRES@
Source/WebKit/wpe/wpe-web-process-extension-uninstalled.pc.in:Requires: glib-2.0 libsoup-@SOUP_API_VERSION@ wpe-1.0
```

**Steps to Reproduce:**

1. Build WebKit at a revision after commit `301131@main`.
2. Attempt to build a third-party application against the installed WebKit using Meson and `pkg-config`. For example, with this `meson.build` file:
   ```meson
   project('foo-launcher', 'c',
     version: '1.0',
     default_options: ['c_std=gnu11'])
   
   webkit2_dep = dependency('wpe-webkit-2.0')
   
   executable('foo-launcher',
     'main.c',
     dependencies: [webkit2_dep])
   ```
3. The build fails during the dependency lookup phase.

**Actual Results:**
The Meson build system fails with the following error because the generated `wpe-webkit-2.0.pc` file contains an invalid requirement for `libsoup-`:

```
| Run-time dependency wpe-webkit-2.0 found: NO
| 
| ../git/meson.build:7:14: ERROR: Dependency lookup for wpe-webkit-2.0 with method 'pkgconfig' failed: Could not generate cflags for wpe-webkit-2.0:
| Package libsoup- was not found in the pkg-config search path.
| Perhaps you should add the directory containing `libsoup-.pc'
| to the PKG_CONFIG_PATH environment variable
| Package 'libsoup-', required by 'wpe-webkit-2.0', not found
```

**Expected Results:**

The build should successfully find the `libsoup-3.0` dependency  from `wpe-webkit-2.0` and compile the third-party application.

[Pablo Saavedra]

Pull request: https://github.com/WebKit/WebKit/pull/52002

[EWS]

Committed 301201@main (bc743a3f24a0): <https://commits.webkit.org/301201@main>

Reviewed commits have been landed. Closing PR #52002 and removing active labels.