Add calculation interpolation migrator.

CONTRIBUTING.md

@@ -55,4 +55,7 @@ non-consensually on open-source code with a variety of licenses, it's not
 obvious that we have the moral or legal right to redistribute code they
 generate.
 
-
+## Testing
+1. Add a directory with the same name as the migrator in `sass/migrator/test/migrators` and
+  add directory to `test/migrators/migrator_dart_test.dart`.
+2. For running all tests: `dart run grinder pkg-compile-snapshot-dev && dart test -x node`

lib/src/migrators/calc_interpolation.dart

@@ -0,0 +1,51 @@
+// Copyright 2022 Google LLC
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'package:sass_api/sass_api.dart';
+
+import '../migration_visitor.dart';
+import '../migrator.dart';
+import '../patch.dart';
+
+/// Removes interpolation in calculation functions.
+class CalculationInterpolationMigrator extends Migrator {
+  final name = "calc-interpolation";
+  final description = r"Removes interpolation in calculation functions"
+      r"`calc()`, `clamp()`, `min()`, and `max()`";
+
+  @override
+  Map<Uri, String> migrateFile(
+      ImportCache importCache, Stylesheet stylesheet, Importer importer) {
+    var visitor = _UnaryMigrationVisitor(importCache, migrateDependencies);
+    var result = visitor.run(stylesheet, importer);
+    missingDependencies.addAll(visitor.missingDependencies);
+    return result;
+  }
+}
+
+class _UnaryMigrationVisitor extends MigrationVisitor {
+  _UnaryMigrationVisitor(ImportCache importCache, bool migrateDependencies)
+      : super(importCache, migrateDependencies);
+
+  @override
+  void visitCalculationExpression(CalculationExpression node) {
+    const calcFunctions = ['calc', 'clamp', 'min', 'max'];
+    final interpolation = RegExp(r'^#{.*\s*}');
+    if (calcFunctions.contains(node.name)) {
+      for (var arg in node.arguments) {
+        for (var match in interpolation.allMatches(arg.toString())) {
+          var noInterpolation = match[0].toString().substring(2, match.end - 1);
+          var interpolationSpan =
+              node.span.file.span(arg.span.start.offset, arg.span.end.offset);
+          if (interpolationSpan.text == match[0].toString()) {
+            addPatch(Patch(interpolationSpan, noInterpolation));
+          }
+        }
+      }
+    }
+    super.visitCalculationExpression(node);
+  }
+}

lib/src/runner.dart

@@ -18,6 +18,7 @@ import 'migrators/media_logic.dart';
 import 'migrators/module.dart';
 import 'migrators/namespace.dart';
 import 'migrators/strict_unary.dart';
+import 'migrators/calc_interpolation.dart';
 import 'exception.dart';
 
 /// A command runner that runs a migrator based on provided arguments.
@@ -59,6 +60,7 @@ class MigratorRunner extends CommandRunner<Map<Uri, String>> {
     addCommand(ModuleMigrator());
     addCommand(NamespaceMigrator());
     addCommand(StrictUnaryMigrator());
+    addCommand(CalculationInterpolationMigrator());
   }
 
   /// Runs a migrator and then writes the migrated files to disk unless

test/migrators/calc_interpolation/calc_remove_interpolation.hrx

@@ -0,0 +1,13 @@
+<==> input/entrypoint.scss
+$c: 1;
+.a { .b: calc(#{$c + 1}); }
+
+// Nested
+.a { .b: calc(max(#{$c, 2})); }
+
+<==> output/entrypoint.scss
+$c: 1;
+.a { .b: calc($c + 1); }
+
+// Nested
+.a { .b: calc(max($c, 2)); }

test/migrators/calc_interpolation/clamp_remove_interpolation.hrx

@@ -0,0 +1,7 @@
+<==> input/entrypoint.scss
+$c: 1;
+.a { .b: clamp(#{$c}); }
+
+<==> output/entrypoint.scss
+$c: 1;
+.a { .b: clamp($c); }

test/migrators/calc_interpolation/max_remove_interpolation.hrx

@@ -0,0 +1,7 @@
+<==> input/entrypoint.scss
+$c: 1;
+.a { .b: max(#{$c, 3}); }
+
+<==> output/entrypoint.scss
+$c: 1;
+.a { .b: max($c, 3); }

test/migrators/calc_interpolation/min_remove_interpolation.hrx

@@ -0,0 +1,7 @@
+<==> input/entrypoint.scss
+$c: 1;
+.a { .b: min(#{$c, 3}); }
+
+<==> output/entrypoint.scss
+$c: 1;
+.a { .b: min($c, 3); }