Add parens around negated variable when namespaced (#115)

Fixes #114.

In fixing this, I also found a fixed a bug when migrating removed color
functions, as a patch to namespace the argument would be applied before
the patch adding the new argument name. This was fixed by ensuring the
arguments of a function expression are visited after the function itself
is patched.

CHANGELOG.md

@@ -8,6 +8,12 @@
   only be considered configured when the configuring declaration is upstream of
   the `!default` declaration.
 
+* When namespacing a negated variable, adds parentheses around it to prevent the
+  `-` from being parsed as part of the namespace.
+
+* Fix a bug in the migrating of removed color functions when the amount is a
+  variable being namespaced.
+
 ## 1.0.0
 
 * Initial release.

lib/src/migrators/module.dart

@@ -522,8 +522,10 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
   /// Adds a namespace to any function call that requires it.
   @override
   void visitFunctionExpression(FunctionExpression node) {
-    super.visitFunctionExpression(node);
-    if (node.namespace != null) return;
+    if (node.namespace != null) {
+      super.visitFunctionExpression(node);
+      return;
+    }
     if (references.sources.containsKey(node)) {
       var declaration = references.functions[node];
       _unreferencable.check(declaration, node);
@@ -561,6 +563,7 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
             ', \$module: "$namespace"'));
       }, getFunctionCall: true);
     }
+    super.visitFunctionExpression(node);
   }
 
   /// Calls [patchNamespace] when the function [node] requires a namespace.
@@ -635,8 +638,13 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
   void _patchRemovedColorFunction(String name, Expression arg,
       {FileSpan existingArgName}) {
     var parameter = removedColorFunctions[name];
-    var needsParens =
-        parameter.endsWith('-') && arg is BinaryOperationExpression;
+    // Surround the argument in parens if negated to avoid `-` being parsed
+    // as part of the namespace.
+    var needsParens = parameter.endsWith('-') &&
+        (arg is BinaryOperationExpression ||
+            arg is FunctionExpression ||
+            (arg is VariableExpression &&
+                references.variables[arg]?.sourceUrl != currentUrl));
     var leftParen = needsParens ? '(' : '';
     if (existingArgName == null) {
       addPatch(patchBefore(arg, '$parameter$leftParen'));
@@ -927,7 +935,12 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
     _renameReference(nameSpan(node), declaration);
     var namespace = _namespaceForDeclaration(declaration);
     if (namespace != null) {
+      // Surround the variable in parens if negated to avoid `-` being parsed
+      // as part of the namespace.
+      var negated = matchesBeforeSpan(node.span, '-');
+      if (negated) addPatch(patchBefore(node, '('));
       addPatch(patchBefore(node, '$namespace.'));
+      if (negated) addPatch(patchAfter(node, ')'));
     }
   }
 

lib/src/utils.dart

@@ -85,6 +85,13 @@ FileSpan extendBackward(FileSpan span, String text) {
   return span.file.span(start - text.length, span.end.offset);
 }
 
+/// Returns true if [span] is preceded by exactly [text].
+bool matchesBeforeSpan(FileSpan span, String text) {
+  var start = span.start.offset;
+  if (start - text.length < 0) return false;
+  return span.file.getText(start - text.length, start) == text;
+}
+
 /// Returns whether [character] is whitespace, according to Sass's definition.
 bool isWhitespace(int character) =>
     character == $space ||

test/migrators/module/namespace_negation.hrx

@@ -0,0 +1,23 @@
+<==> arguments
+--migrate-deps
+
+<==> input/entrypoint.scss
+@import "library";
+a {
+  b: -$amount;
+  color: darken($color, $amount);
+  background: darken($color, fn());
+}
+
+<==> input/_library.scss
+$color: blue;
+$amount: 10%;
+
+<==> output/entrypoint.scss
+@use "sass:color";
+@use "library";
+a {
+  b: -(library.$amount);
+  color: color.adjust(library.$color, $lightness: -(library.$amount));
+  background: color.adjust(library.$color, $lightness: -(fn()));
+}