rust: Accept generated sources for main.rs

There are still caveats here. Rust/cargo handles generated sources by
writing out all targets of a single repo into a single output directory,
setting a path to that via a build-time environment variable, and then
include those files via a set of functions and macros. Meson's build
layout is naturally different, and ninja makes working with environment
variables at compile time difficult.

Fixes #8157

2 files changed, 32 insertions, 0 deletions

diff --git a/test cases/rust/11 generated main/gen.py b/test cases/rust/11 generated main/gen.py
new file mode 100644
index 000000000..ebbc2a7a6
--- /dev/null
+++ b/test cases/rust/11 generated main/gen.py
@@ -0,0 +1,16 @@
+#!/usr/bin/env python3
+
+import argparse
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('out')
+    args = parser.parse_args()
+
+    with open(args.out, 'w') as f:
+        f.write('fn main() { println!("I prefer tarnish, actually.") }')
+
+
+if __name__ == "__main__":
+    main()
diff --git a/test cases/rust/11 generated main/meson.build b/test cases/rust/11 generated main/meson.build
new file mode 100644
index 000000000..474981658
--- /dev/null
+++ b/test cases/rust/11 generated main/meson.build
@@ -0,0 +1,16 @@
+project('generated rust main', 'rust')
+
+gen = find_program('gen.py')
+
+c = custom_target(
+  'custom_target',
+  command : [gen, '@OUTPUT@'],
+  output : ['main.rs'],
+)
+
+executable('custom_target_main', c)
+executable('custom_target_index_main', c[0])
+
+gen = generator(gen, arguments : ['@OUTPUT@'], output : '@BASENAME@.rs')
+# Doesn't actually use gen.py as input, just a limitation of generators
+executable('generator_main', gen.process(['gen.py']))