protoc: simplify the java generation also solving problems with .proto input files generated during build

playground/protoc_gen_java/proto.source

@@ -0,0 +1,14 @@
+package udp.tc.tests;
+
+option java_package = "com.udp.tc.tests";
+option java_outer_classname = "MessageInc";
+option cc_generic_services = false;
+option java_generic_services = false;
+option py_generic_services = false;
+
+
+message IncludeMe {
+    required int32 test = 1;
+    optional uint32 blah = 2;
+    optional uint32 justinc = 3;
+}

playground/protoc_gen_java/wscript

@@ -0,0 +1,51 @@
+#! /usr/bin/env python
+# encoding: utf-8
+# Federico Pellegrin, 2019 (fedepell)
+
+import os
+from waflib import Logs
+
+top = '.'
+out = 'build'
+
+def options(opt):
+	opt.load('compiler_cxx java')
+
+def configure(conf):
+	conf.load('compiler_cxx java protoc')
+	# Here you have to point to your protobuf-java JAR
+	conf.env.CLASSPATH_PROTOBUF = ['/usr/share/maven-repo/com/google/protobuf/protobuf-java/3.0.0/protobuf-java-3.0.0.jar']
+
+def build(bld):
+
+	# this simulates a .proto generator. the gen.proto is generated in build
+	genp = bld(
+		rule = "cp ${SRC} ${TGT}",
+		source = "proto.source",
+		target = "inc/gen.proto"
+	)
+
+	# cxx doesn't have a problem with this, just knows gen.proto will pop up later
+        bld(
+		features = 'cxx cxxshlib',
+		source = [ bld.path.find_or_declare(genp.target) ],
+                name     = 'somelib',
+                target   = 'somelib'
+	)
+
+	# but for java:
+
+	# we either put grouping because of protoc java generations needs .proto to generate out fname (#2218)
+	# or accept that java dep is not strict on the .java file name (but relies just on explicit task ordering)
+	# bld.add_group()
+
+	# inc/gen.proto is an implicit dependency, but the file is generated at
+	# build time while protoc extra uses it before to determine the .java file
+	# name that will get generated
+	bld(
+		features = 'javac protoc',
+		name = 'pbjava',
+		srcdir = bld.path.find_or_declare(genp.target).parent,
+		source   = [ bld.path.find_or_declare(genp.target) ],
+		use = 'PROTOBUF',
+	)

waflib/extras/protoc.py

@@ -6,7 +6,7 @@
 import re, os
 from waflib.Task import Task
 from waflib.TaskGen import extension
-from waflib import Errors, Context
+from waflib import Errors, Context, Logs
 
 """
 A simple tool to integrate protocol buffers into your build system.
@@ -169,64 +169,12 @@ def process_protoc(self, node):
 		out_nodes.append(py_node)
 		protoc_flags.append('--python_out=%s' % node.parent.get_bld().bldpath())
 
-	if 'javac' in self.features and node.exists():
+	if 'javac' in self.features:
-		pkgname, javapkg, javacn, nodename = None, None, None, None
-		messages = []
-
-		# .java file name is done with some rules depending on .proto file content:
-		#   -) package is either derived from option java_package if present
-		#      or from package directive
-		#   -) file name is either derived from option java_outer_classname if present
-		#      or the .proto file is converted to camelcase. If a message
-		#      is named the same then the behaviour depends on protoc version
-		#
-		# See also: https://developers.google.com/protocol-buffers/docs/reference/java-generated#invocation
-
-		code = node.read().splitlines()
-		for line in code:
-			m = re.search(r'^package\s+(.*);', line)
-			if m:
-				pkgname = m.groups()[0]
-			m = re.search(r'^option\s+(\S*)\s*=\s*"(\S*)";', line)
-			if m:
-				optname = m.groups()[0]
-				if optname == 'java_package':
-					javapkg = m.groups()[1]
-				elif optname == 'java_outer_classname':
-					javacn = m.groups()[1]
-			if self.env.PROTOC_MAJOR > '2':
-				m = re.search(r'^message\s+(\w*)\s*{*', line)
-				if m:
-					messages.append(m.groups()[0])
-
-		if javapkg:
-			nodename = javapkg
-		elif pkgname:
-			nodename = pkgname
-		else:
-			raise Errors.WafError('Cannot derive java name from protoc file')
-
-		nodename = nodename.replace('.',os.sep) + os.sep
-		if javacn:
-			nodename += javacn + '.java'
-		else:
-			filenamebase = node.abspath()[node.abspath().rfind(os.sep)+1:node.abspath().rfind('.')].replace('_','')
-			filenamebase = filenamebase[:1].upper() + filenamebase[1:]
-			if self.env.PROTOC_MAJOR > '2' and node.abspath()[node.abspath().rfind(os.sep)+1:node.abspath().rfind('.')].title() in messages:
-				nodename += filenamebase + 'OuterClass.java'
-			else:
-				nodename += filenamebase + '.java'
-
-		java_node = node.parent.find_or_declare(nodename)
-		out_nodes.append(java_node)
-		protoc_flags.append('--java_out=%s' % node.parent.get_bld().bldpath())
-
 		# Make javac get also pick java code generated in build
 		if not node.parent.get_bld() in self.javac_task.srcdir:
 			self.javac_task.srcdir.append(node.parent.get_bld())
 
-	if not out_nodes and node.exists():
+		protoc_flags.append('--java_out=%s' % node.parent.get_bld().bldpath())
-		raise Errors.WafError('Feature %r not supported by protoc extra' % self.features)
 
 	tsk = self.create_task('protoc', node, out_nodes)
 	tsk.env.append_value('PROTOC_FLAGS', protoc_flags)