SERVER-17919 Add support for emitting a compilation database

1 files changed, 156 insertions, 0 deletions

diff --git a/site_scons/site_tools/compilation_db.py b/site_scons/site_tools/compilation_db.py
new file mode 100644
index 00000000000..283487cda17
--- /dev/null
+++ b/site_scons/site_tools/compilation_db.py
@@ -0,0 +1,156 @@
+# Copyright (C) 2015 MongoDB Inc.
+#
+# This program is free software: you can redistribute it and/or  modify
+# it under the terms of the GNU Affero General Public License, version 3,
+# as published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import json
+import SCons
+import itertools
+
+# Implements the ability for SCons to emit a compilation database for the MongoDB project. See
+# http://clang.llvm.org/docs/JSONCompilationDatabase.html for details on what a compilation
+# database is, and why you might want one. The only user visible entry point here is
+# 'env.CompilationDatabase'. This method takes an optional 'target' to name the file that
+# should hold the compilation database, otherwise, the file defaults to compile_commands.json,
+# which is the name that most clang tools search for by default.
+
+# TODO: Is there a better way to do this than this global? Right now this exists so that the
+# emitter we add can record all of the things it emits, so that the scanner for the top level
+# compilation database can access the complete list, and also so that the writer has easy
+# access to write all of the files. But it seems clunky. How can the emitter and the scanner
+# communicate more gracefully?
+__COMPILATION_DB_ENTRIES=[]
+
+# We make no effort to avoid rebuilding the entries. Someday, perhaps we could and even
+# integrate with the cache, but there doesn't seem to be much call for it.
+class __CompilationDbNode(SCons.Node.Node):
+    def __init__(self):
+        SCons.Node.Node.__init__(self)
+
+    def changed_since_last_build(self, target, prev_ni):
+        return True
+
+def makeEmitCompilationDbEntry(comstr):
+    user_action = SCons.Action.Action(comstr)
+    def EmitCompilationDbEntry(target, source, env):
+
+        dbtarget = __CompilationDbNode()
+
+        entry = env.__COMPILATIONDB_Entry(
+            target=dbtarget,
+            source=[],
+            __COMPILATIONDB_UTARGET=target,
+            __COMPILATIONDB_USOURCE=source,
+            __COMPILATIONDB_UACTION=user_action)
+
+        # TODO: Technically, these next two lines should not be required: it should be fine to
+        # cache the entries. However, they don't seem to update properly. Since they are quick
+        # to re-generate disable caching and sidestep this problem.
+        env.AlwaysBuild(entry)
+        env.NoCache(entry)
+
+        __COMPILATION_DB_ENTRIES.append(dbtarget)
+
+        return target, source
+
+    return EmitCompilationDbEntry
+
+def CompilationDbEntryAction(target, source, env, **kw):
+
+    command = env['__COMPILATIONDB_UACTION'].strfunction(
+        target=env['__COMPILATIONDB_UTARGET'],
+        source=env['__COMPILATIONDB_USOURCE'],
+        env=env)
+
+    entry = {
+        "directory": env.Dir('#').abspath,
+        "command": command,
+        "file": str(env['__COMPILATIONDB_USOURCE'][0])
+    }
+
+    setattr(target[0], '__COMPILATION_DB_ENTRY', entry)
+
+def WriteCompilationDb(target, source, env):
+    entries = []
+
+    for s in __COMPILATION_DB_ENTRIES:
+        entries.append(getattr(s, '__COMPILATION_DB_ENTRY'))
+
+    with open(str(target[0]), 'w') as target_file:
+        json.dump(entries, target_file,
+                  sort_keys=True,
+                  indent=4,
+                  separators=(',', ': '))
+
+def ScanCompilationDb(node, env, path):
+    return __COMPILATION_DB_ENTRIES
+
+def generate(env, **kwargs):
+
+    static_obj, shared_obj = SCons.Tool.createObjBuilders(env)
+
+    # TODO: Is there a way to obtain the configured suffixes for C and C++
+    # from the existing obj builders? Seems unfortunate to re-iterate them.
+    CSuffixes = ['.c']
+    CXXSuffixes = ['.cc', '.cxx', '.cpp']
+
+    env['COMPILATIONDB_COMSTR'] = kwargs.get(
+        'COMPILATIONDB_COMSTR', 'Building compilation database $TARGET')
+
+    components_by_suffix = itertools.chain(
+        itertools.product(CSuffixes, [
+            (static_obj, SCons.Defaults.StaticObjectEmitter, '$CCCOM'),
+            (shared_obj, SCons.Defaults.SharedObjectEmitter, '$SHCCCOM'),
+        ]),
+        itertools.product(CXXSuffixes, [
+            (static_obj, SCons.Defaults.StaticObjectEmitter, '$CXXCOM'),
+            (shared_obj, SCons.Defaults.SharedObjectEmitter, '$SHCXXCOM'),
+        ]),
+    )
+
+    for entry in components_by_suffix:
+        suffix = entry[0]
+        builder, base_emitter, command = entry[1]
+
+        builder.add_emitter(
+            suffix, SCons.Builder.ListEmitter(
+                [
+                    makeEmitCompilationDbEntry(command),
+                    base_emitter,
+                ]
+            ))
+
+    env['BUILDERS']['__COMPILATIONDB_Entry'] = SCons.Builder.Builder(
+        action=SCons.Action.Action(CompilationDbEntryAction, None),
+    )
+
+    env['BUILDERS']['__COMPILATIONDB_Database'] = SCons.Builder.Builder(
+        action=SCons.Action.Action(WriteCompilationDb, "$COMPILATIONDB_COMSTR"),
+        target_scanner=SCons.Scanner.Scanner(
+            function=ScanCompilationDb,
+            node_class=None)
+    )
+
+    def CompilationDatabase(env, target):
+        result = env.__COMPILATIONDB_Database(
+            target=target,
+            source=[])
+
+        env.AlwaysBuild(result)
+        env.NoCache(result)
+
+        return result
+
+    env.AddMethod(CompilationDatabase, 'CompilationDatabase')
+
+def exists(env):
+    return True