workspace concretize: define missing variables and expand software specs

Fixes an issue where running 'ramble workspace concretize' failed with a
schema ValidationError (CommentedMap is not of type 'string') when compiler
or software specs contained variable templates (e.g., {system_compiler_spec}).

Key changes:
- Call app_inst.define_missing_variables() during concretize to ensure
  system, platform, and modifier variables are registered in app_inst.variables.
- Add _expand_software_spec() to expand template variables in SoftwareSpec
  instances (pkg_spec, compiler_spec, compiler) for both compilers and specs.
- Add regression unit tests with mock application and modifier in
  workspace_concretize.py.

Signed-off-by: Ching-Lung Hsu <chinglunghsu@google.com>

Author: chinglung880218

lib/ramble/ramble/test/cmd/workspace_concretize.py

@@ -136,3 +136,41 @@ def test_workspace_concretize_populated_env_no_warning(workspace_name, capsys):
     workspace("concretize", global_args=global_args)
     captured = capsys.readouterr()
     assert "was auto-constructed" not in captured.err
+
+
+def test_workspace_concretize_expand_software_spec_variables(
+    workspace_name, mock_applications, mock_modifiers
+):
+    ws = ramble.workspace.create(workspace_name)
+    global_args = ["-w", workspace_name]
+
+    workspace(
+        "manage",
+        "experiments",
+        "var-compiler-app",
+        "-V",
+        "package_manager=spack",
+        global_args=global_args,
+    )
+    workspace(
+        "manage",
+        "modifiers",
+        "--add",
+        "--name",
+        "var-compiler-mod",
+        "--scope",
+        "workspace",
+        global_args=global_args,
+    )
+    workspace("concretize", global_args=global_args)
+
+    with open(ws.config_file_path, encoding="utf-8") as f:
+        content = f.read()
+        assert "var-compiler" in content
+        assert "gcc@12.2.0" in content
+        assert "{my_compiler_spec}" not in content
+        assert "var-pkg" in content
+        assert "zlib@1.2.13" in content
+        assert "mod-compiler" in content
+        assert "gcc@13.1.0" in content
+        assert "{mod_compiler_spec}" not in content

lib/ramble/ramble/workspace/workspace.py

@@ -1515,9 +1515,19 @@ def concretize(self, force=False, quiet=False):
 
         force_prefix = force_prefix or len(pkgman_prefixes) > 1
 
+        def _expand_software_spec(spec, expander):
+            """Expand template variables in a SoftwareSpec instance."""
+            if spec.pkg_spec:
+                spec.pkg_spec = expander.expand_var(spec.pkg_spec)
+            if spec.compiler_spec:
+                spec.compiler_spec = expander.expand_var(spec.compiler_spec)
+            if spec.compiler:
+                spec.compiler = expander.expand_var(spec.compiler)
+
         for _, app_inst, _ in experiment_set.all_experiments():
             app_inst.build_modifier_instances()
             app_inst.define_variables_for_template_path()
+            app_inst.define_missing_variables()
             env_name_str = app_inst.expander.expansion_str(ramble.keywords.keywords.env_name)
             env_name = app_inst.expander.expand_var(env_name_str)
 
@@ -1529,6 +1539,8 @@ def concretize(self, force=False, quiet=False):
             )
             for comp, definitions in compiler_packages.items():
                 for info in definitions:
+                    _expand_software_spec(info, app_inst.expander)
+
                     if (
                         not quiet
                         and comp in packages_dict

var/ramble/repos/builtin.mock/applications/var-compiler-app/application.py

@@ -0,0 +1,37 @@
+# Copyright 2022-2026 The Ramble Authors
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+from ramble.appkit import *
+
+
+class VarCompilerApp(ExecutableApplication):
+    """Test application to verify concretize variable expansion in specs"""
+
+    name = "var-compiler-app"
+
+    executable("echo", "echo", use_mpi=False)
+    workload("test_wl", executable="echo")
+
+    workload_variable(
+        "my_compiler_spec",
+        default="gcc@12.2.0",
+        description="Compiler spec variable",
+        workloads=["test_wl"],
+    )
+
+    define_compiler(
+        "var-compiler",
+        pkg_spec="{my_compiler_spec}",
+        compiler_spec="{my_compiler_spec}",
+    )
+
+    software_spec(
+        "var-pkg",
+        pkg_spec="zlib@1.2.13",
+        compiler="var-compiler",
+    )

var/ramble/repos/builtin.mock/modifiers/var-compiler-mod/modifier.py

@@ -0,0 +1,33 @@
+# Copyright 2022-2026 The Ramble Authors
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+from ramble.modkit import *
+
+
+class VarCompilerMod(BasicModifier):
+    """Mock modifier to test concretize variable expansion in compiler specs"""
+
+    name = "var-compiler-mod"
+    tags("test")
+
+    mode("test_mode", description="A test mode")
+    default_mode("test_mode")
+
+    variable(
+        "mod_compiler_spec",
+        default="gcc@13.1.0",
+        description="Compiler spec defined in modifier",
+        modes=["test_mode"],
+    )
+
+    with when("package_manager_family=spack"):
+        define_compiler(
+            "mod-compiler",
+            pkg_spec="{mod_compiler_spec}",
+            compiler_spec="{mod_compiler_spec}",
+        )