From d53f6129f48e1c0ed755e4aedda0085a528a1426 Mon Sep 17 00:00:00 2001
From: William Deegan <bill@baddogconsulting.com>
Date: Sat, 6 Jun 2020 11:28:41 -0700
Subject: change CompilationDatabase from psuedo builder to builder. Add
 emitter to clear source and set default target as 'compile_commands.json'.

---
 CHANGES.txt                                 |  1 +
 SCons/Tool/compilation_db.py                | 21 +++++++++++++--------
 SCons/Tool/compilation_db.xml               |  8 +++++---
 doc/user/misc.xml                           | 15 +++++++++++++++
 test/CompilationDatabase/fixture/SConstruct |  4 ++--
 5 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 414825d..b04615f 100755
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -56,6 +56,7 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Renamed as.py to asm.py and left redirecting tool.  'as' is a reserved word and so
       changing the name was required as we wanted to import symbols for use in compilation_db
       tool.
+    - Add CompilationDatabase() builder in compilation_db tool. Contributed by MongoDB.
 
   From Jeremy Elson:
     - Updated design doc to use the correct syntax for Depends()
diff --git a/SCons/Tool/compilation_db.py b/SCons/Tool/compilation_db.py
index 0b7c9b8..788f454 100644
--- a/SCons/Tool/compilation_db.py
+++ b/SCons/Tool/compilation_db.py
@@ -154,13 +154,18 @@ def scan_compilation_db(node, env, path):
     return __COMPILATION_DB_ENTRIES
 
 
-def CompilationDatabase(env, target='compile_commands.json'):
-    result = env.__COMPILATIONDB_Database(target=target, source=[])
+def compilation_db_emitter(target, source, env):
+    """ fix up the source/targets """
 
-    env.AlwaysBuild(result)
-    env.NoCache(result)
+    # Default target name is compilation_db.json
+    if not target:
+        target = ['compile_commands.json', ]
 
-    return result
+    # No source should have been passed. Drop it.
+    if source:
+        source = []
+
+    return target, source
 
 
 def generate(env, **kwargs):
@@ -214,17 +219,17 @@ def generate(env, **kwargs):
         action=SCons.Action.Action(compilation_db_entry_action, None),
     )
 
-    env["BUILDERS"]["__COMPILATIONDB_Database"] = SCons.Builder.Builder(
+    env["BUILDERS"]["CompilationDatabase"] = SCons.Builder.Builder(
         action=SCons.Action.Action(write_compilation_db, "$COMPILATIONDB_COMSTR"),
         target_scanner=SCons.Scanner.Scanner(
             function=scan_compilation_db, node_class=None
         ),
+        emitter=compilation_db_emitter,
+        suffix='json',
     )
 
     env['COMPILATIONDB_USE_ABSPATH'] = False
 
-    env.AddMethod(CompilationDatabase, "CompilationDatabase")
-
 
 def exists(env):
     return True
diff --git a/SCons/Tool/compilation_db.xml b/SCons/Tool/compilation_db.xml
index 65b557b..12a4db0 100644
--- a/SCons/Tool/compilation_db.xml
+++ b/SCons/Tool/compilation_db.xml
@@ -26,12 +26,14 @@ See its __doc__ string for a discussion of the format.
     <tool name="compilation_db">
         <summary>
             <para>
-                Sets up &b-CompilationDatabase; Pseudo builder.
+                Sets up &b-CompilationDatabase; builder.
             </para>
             <para>
                 This builder generates a clang tooling compatible compilation database.
-                Note: If there's no specified target file, it will default to
-                <filename>compile_commands.json</filename>
+            </para>
+            <para>
+                Note: The target file is typically named
+                <filename>compile_commands.json</filename>.
             </para>
         </summary>
         <sets>
diff --git a/doc/user/misc.xml b/doc/user/misc.xml
index e9b078d..8aa7d62 100644
--- a/doc/user/misc.xml
+++ b/doc/user/misc.xml
@@ -699,9 +699,17 @@ env.Command('directory_build_info',
         </para>
         <para>This is controlled by
             <envar>COMPILATIONDB_USE_ABSPATH=(True|False)</envar>
+            which defaults to False.
         </para>
 
         <para>Example of absolute paths for target and source</para>
+
+        <sconstruct>
+env = Environment(COMPILATIONDB_USE_ABSPATH=True)
+env.Tool('compilation_db')
+env.CompilationDatabase('compile_commands.json')
+        </sconstruct>
+
         <programlisting language="json">
 [
     {
@@ -712,8 +720,15 @@ env.Command('directory_build_info',
     }
 ]
         </programlisting>
+
+
         <para>Example of relative paths for target and source</para>
 
+        <sconstruct>
+env = Environment()
+env.Tool('compilation_db')
+env.CompilationDatabase('compile_commands.json')
+        </sconstruct>
         <programlisting language="json">
 [
     {
diff --git a/test/CompilationDatabase/fixture/SConstruct b/test/CompilationDatabase/fixture/SConstruct
index 0f8944e..0bbcafa 100644
--- a/test/CompilationDatabase/fixture/SConstruct
+++ b/test/CompilationDatabase/fixture/SConstruct
@@ -12,8 +12,8 @@ env.Tool('compilation_db')
 
 if ARGUMENTS.get('ABSPATH', False):
     env['COMPILATIONDB_USE_ABSPATH'] = True
-    env.CompilationDatabase('compile_commands_abs.json')
+    env.CompilationDatabase('compile_commands_abs.json', source=[])
 else:
-    env.CompilationDatabase('compile_commands.json')
+    env.CompilationDatabase('compile_commands.json', source=[])
 
 env.Program('main', 'test_main.c')
-- 
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