Fix envoy_proto_descriptor to compute protobuf include path dynamically

Use bash parameter expansion to extract the protobuf src directory path
at build time from the location of any.proto. This makes it work in both
WORKSPACE mode (external/com_google_protobuf/src) and bzlmod mode
(external/protobuf~/src) without hardcoding paths.

Co-authored-by: phlax <454682+phlax@users.noreply.github.com>
Signed-off-by: Ryan Northey <ryan@synca.io>

Author: Copilot

bazel/envoy_build_system.bzl

@@ -200,6 +200,10 @@ def envoy_cc_platform_specific_dep(name):
 def envoy_proto_descriptor(name, out, srcs = [], external_deps = []):
     input_files = ["$(location " + src + ")" for src in srcs]
     include_paths = [".", native.package_name()]
+    
+    # Track whether we need to compute protobuf include path dynamically
+    has_protobuf_deps = False
+    protobuf_include_marker = None
 
     if "api_httpbody_protos" in external_deps:
         srcs.append("@com_google_googleapis//google/api:httpbody.proto")
@@ -226,13 +230,34 @@ def envoy_proto_descriptor(name, out, srcs = [], external_deps = []):
         srcs.append("@com_google_protobuf//src/google/protobuf:type.proto")
         srcs.append("@com_google_protobuf//src/google/protobuf:wrappers.proto")
         srcs.append("@com_google_protobuf//src/google/protobuf/compiler:plugin.proto")
-        include_paths.append("external/com_google_protobuf/src")
+        has_protobuf_deps = True
+        # Use any.proto as a marker to compute the include path dynamically
+        protobuf_include_marker = "@com_google_protobuf//src/google/protobuf:any.proto"
 
     options = ["--include_imports"]
-    options.extend(["-I" + include_path for include_path in include_paths])
-    options.append("--descriptor_set_out=$@")
-
-    cmd = "$(location @com_google_protobuf//:protoc) " + " ".join(options + input_files)
+    
+    # Build the command that computes include paths dynamically at execution time
+    if has_protobuf_deps and protobuf_include_marker:
+        # Extract the directory containing the protobuf proto files at build time
+        # The proto files are in external/com_google_protobuf~/src/google/protobuf/
+        # We need to extract up to the /src part
+        cmd_parts = []
+        # Get the full path to any.proto, then extract everything before /google/protobuf/
+        cmd_parts.append("ANY_PROTO_PATH=$(location " + protobuf_include_marker + ")")
+        cmd_parts.append("PROTOBUF_INCLUDE_PATH=$${ANY_PROTO_PATH%/google/protobuf/*}")
+        cmd_parts.append("INCLUDE_OPTS=\"--include_imports\"")
+        
+        # Add all include paths
+        for include_path in include_paths:
+            cmd_parts.append("INCLUDE_OPTS=\"$$INCLUDE_OPTS -I" + include_path + "\"")
+        cmd_parts.append("INCLUDE_OPTS=\"$$INCLUDE_OPTS -I$$PROTOBUF_INCLUDE_PATH\"")
+        
+        cmd_parts.append("$(location @com_google_protobuf//:protoc) $$INCLUDE_OPTS --descriptor_set_out=$@ " + " ".join(input_files))
+        cmd = " && ".join(cmd_parts)
+    else:
+        options.extend(["-I" + include_path for include_path in include_paths])
+        options.append("--descriptor_set_out=$@")
+        cmd = "$(location @com_google_protobuf//:protoc) " + " ".join(options + input_files)
     native.genrule(
         name = name,
         srcs = srcs,