SERVER-50376 Ninja should rebuild on compiler and tool changes

Allow Ninja to rebuild build.ninja any time a SCons tool or the compiler
is changed between iterative rebuilds. This change allows us to ensure
that we don't have any stale object files lying around that may have
been produced by an incompatible toolchain.

2 files changed, 25 insertions, 9 deletions

diff --git a/site_scons/site_tools/next/icecream.py b/site_scons/site_tools/next/icecream.py
index b1fb49543b5..7456ed0cc8f 100644
--- a/site_scons/site_tools/next/icecream.py
+++ b/site_scons/site_tools/next/icecream.py
@@ -283,7 +283,7 @@ def generate(env):
         )
     ))
 
-    # We can't allow these to interact with the cache beacuse the
+    # We can't allow these to interact with the cache because the
     # second action produces a file unknown to SCons. If caching were
     # permitted, the other two files could be retrieved from cache but
     # the file produced by the second action could not (and would not)
@@ -368,6 +368,14 @@ def generate(env):
             # This dependency is necessary so that we build into this
             # string before we create the file.
             icecc_version_string_value,
+
+            # TODO: SERVER-50587 We need to make explicit depends here because of NINJA_SKIP. Any
+            # dependencies in the nodes created in setupEnv with NINJA_SKIP would have
+            # that dependency chain hidden from ninja, so they won't be rebuilt unless
+            # added as dependencies here on this node that has NINJA_SKIP=False.
+            '$CC',
+            '$CXX',
+            icecc_version_file,
         ],
     )
 
diff --git a/site_scons/site_tools/next/ninja.py b/site_scons/site_tools/next/ninja.py
index 0506fa658ef..5a5dcf84aed 100644
--- a/site_scons/site_tools/next/ninja.py
+++ b/site_scons/site_tools/next/ninja.py
@@ -996,7 +996,7 @@ def gen_get_response_file_command(env, rule, tool, tool_is_dynamic=False):
         variables[rule] = cmd
         if use_command_env:
             variables["env"] = get_command_env(env)
-        return rule, variables
+        return rule, variables, [tool_command]
 
     return get_response_file_command
 
@@ -1026,13 +1026,21 @@ def generate_command(env, node, action, targets, sources, executor=None):
     return cmd.replace("$", "$$")
 
 
-def get_shell_command(env, node, action, targets, sources, executor=None):
+def get_generic_shell_command(env, node, action, targets, sources, executor=None):
     return (
         "CMD",
         {
             "cmd": generate_command(env, node, action, targets, sources, executor=None),
             "env": get_command_env(env),
         },
+        # Since this function is a rule mapping provider, it must return a list of dependencies,
+        # and usually this would be the path to a tool, such as a compiler, used for this rule.
+        # However this function is to generic to be able to reliably extract such deps
+        # from the command, so we return a placeholder empty list. It should be noted that
+        # generally this function will not be used soley and is more like a template to generate
+        # the basics for a custom provider which may have more specific options for a provier
+        # function for a custom NinjaRuleMapping.
+        []
     )
 
 
@@ -1068,12 +1076,12 @@ def get_command(env, node, action):  # pylint: disable=too-many-branches
     if not comstr:
         return None
 
-    provider = __NINJA_RULE_MAPPING.get(comstr, get_shell_command)
-    rule, variables = provider(sub_env, node, action, tlist, slist, executor=executor)
+    provider = __NINJA_RULE_MAPPING.get(comstr, get_generic_shell_command)
+    rule, variables, provider_deps = provider(sub_env, node, action, tlist, slist, executor=executor)
 
     # Get the dependencies for all targets
     implicit = list({dep for tgt in tlist for dep in get_dependencies(tgt)})
-
+    implicit.extend(provider_deps)
     ninja_build = {
         "order_only": get_order_only(node),
         "outputs": get_outputs(node),
@@ -1136,7 +1144,7 @@ def register_custom_handler(env, name, handler):
 
 
 def register_custom_rule_mapping(env, pre_subst_string, rule):
-    """Register a custom handler for SCons function actions."""
+    """Register a function to call for a given rule."""
     global __NINJA_RULE_MAPPING
     __NINJA_RULE_MAPPING[pre_subst_string] = rule
 
@@ -1149,7 +1157,7 @@ def register_custom_rule(env, rule, command, description="", deps=None, pool=Non
     }
 
     if use_depfile:
-        rule_obj["depfile"] = os.path.join(get_path(env['NINJA_BUILDDIR']),'$out.depfile')
+        rule_obj["depfile"] = os.path.join(get_path(env['NINJA_BUILDDIR']), '$out.depfile')
 
     if deps is not None:
         rule_obj["deps"] = deps
@@ -1344,7 +1352,7 @@ def generate(env):
 
     # Provide a way for custom rule authors to easily access command
     # generation.
-    env.AddMethod(get_shell_command, "NinjaGetShellCommand")
+    env.AddMethod(get_generic_shell_command, "NinjaGetGenericShellCommand")
     env.AddMethod(gen_get_response_file_command, "NinjaGenResponseFileProvider")
 
     # Provides a way for users to handle custom FunctionActions they