build: add capnp compiler wrapper

we need this to generate dependency information, and it'll be the entry
point for custom codegen once we need it. a wrapper also makes it a lot
easier to generate a whole namespace's worth of rpc definitions at once

Change-Id: Iba7a1c92a8a40bede9ed71aa3ab455477ff5e568

lix/code-generation/capnpc_wrapper.py

@@ -0,0 +1,64 @@
+#!@python@
+
+import argparse
+import capnp
+from pathlib import Path
+import os
+import subprocess
+import sys
+
+if lang := os.environ.get('lix_capnp_lang'):
+    outputs = os.environ['lix_capnp_outputs'].split()
+    old_cwd = os.environ['lix_capnp_old_cwd']
+    schema = capnp.load('@capnp_include@/capnp/schema.capnp', imports=['@capnp_include@'])
+    request = schema.CodeGeneratorRequest.read(sys.stdin)
+
+    subprocess.run([lang], input=request.as_builder().to_bytes()).check_returncode()
+
+    base_dir = os.getcwd()
+    os.chdir(old_cwd)
+
+    include = [ str(Path(p).resolve()) for p in os.environ['lix_capnp_include'].split(':') ]
+
+    if depfile := os.environ['lix_capnp_depfile']:
+        deps = ""
+        for input in request.requestedFiles:
+            deps += " ".join(f"{input.filename}.{o}" for o in outputs)
+            deps += ":"
+            for dep in input.imports:
+                if dep.name.startswith("/"):
+                    for candidate in (Path(i + dep.name) for i in include):
+                        if candidate.exists():
+                            deps += " " + str(candidate)
+                            break
+                else:
+                    raise RuntimeError("not handling relative includes")
+            deps += "\n\n"
+        Path(depfile).write_text(deps)
+else:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--language')
+    parser.add_argument('--outdir')
+    parser.add_argument('--src-prefix')
+    parser.add_argument('--depfile', default="")
+    parser.add_argument('-I', '--include', action='append', default=['@capnp_include@'])
+    parser.add_argument('inputs', nargs='+')
+    args = parser.parse_args()
+
+    for infile in args.inputs:
+        os.environ['lix_capnp_lang'] = f"capnpc-{args.language}"
+        os.environ['lix_capnp_include'] = ':'.join(args.include)
+        os.environ['lix_capnp_depfile'] = args.depfile
+        os.environ['lix_capnp_old_cwd'] = os.getcwd()
+        if args.language == "c++":
+            os.environ['lix_capnp_outputs'] = "c++ h"
+        else:
+            raise RuntimeError("unknown language " + args.language)
+        subprocess.run([
+            '@capnp@',
+            'compile',
+            f'-o{sys.argv[0]}:{args.outdir}',
+            f'--src-prefix={args.src_prefix}',
+            *(f"-I{i}" for i in args.include),
+            infile
+        ]).check_returncode()

meson.build

@@ -248,6 +248,7 @@ configdata += {
 
 boost = dependency('boost', required : true, modules : ['container'], include_type : 'system')
 kj = dependency('kj-async', required : true, include_type : 'system')
+capnp_rpc = dependency('capnp-rpc', required : true, include_type : 'system')
 
 # cpuid only makes sense on x86_64
 cpuid_required = is_x64 ? get_option('cpuid') : false
@@ -628,6 +629,21 @@ if is_darwin
   )
 endif
 
+capnpc_wrapper = custom_target(
+  'capnpc_wrapper',
+  command : ['cp', '@INPUT@', '@OUTPUT@'],
+  input : configure_file(
+    input : 'lix/code-generation/capnpc_wrapper.py',
+    output : 'capnpc_wrapper.configured',
+    configuration : {
+      'capnp_include' : capnp_rpc.get_variable(pkgconfig : 'includedir'),
+      'capnp' : find_program('capnp', required : true, native : true).full_path(),
+      'python' : python.full_path(),
+    },
+  ),
+  output : 'capnpc_wrapper',
+)
+
 subdir('lix')
 subdir('scripts')
 subdir('misc')

meson/clang-tidy/build_required_targets.py

@@ -14,8 +14,16 @@ def main():
 
     args = ap.parse_args()
 
-    targets = [t for t in get_targets_of_rule(args.build_root, 'CUSTOM_COMMAND') if t.endswith('.gen.hh')]
-    targets += [t for t in get_targets_of_rule(args.build_root, 'CUSTOM_COMMAND') if t.endswith('.gen.inc')]
+    targets = [
+        t for t in get_targets_of_rule(args.build_root, 'CUSTOM_COMMAND')
+        if t.endswith('.gen.hh')
+    ] + [
+        t for t in get_targets_of_rule(args.build_root, 'CUSTOM_COMMAND_DEP')
+        if t.endswith('.capnp.h')
+    ] + [
+        t for t in get_targets_of_rule(args.build_root, 'CUSTOM_COMMAND')
+        if t.endswith('.gen.inc')
+    ]
     ninja_build(args.build_root, targets)
 
 if __name__ == '__main__':

package.nix

@@ -208,6 +208,7 @@ stdenv.mkDerivation (finalAttrs: {
     p:
     [
       p.python-frontmatter
+      p.pycapnp
     ]
     ++ lib.optionals finalAttrs.doCheck [
       p.pytest
@@ -560,6 +561,7 @@ stdenv.mkDerivation (finalAttrs: {
             p.aiohttp
             p.python-frontmatter
             p.toml
+            p.pycapnp
 
             p.yapf
             p.requests