Implement contracts

Author: TrySound

src/index.js

@@ -117,18 +117,42 @@ const addExports = (css, aliases) => {
   css.prepend(createICSSRules(icssImports, exports));
 };
 
-module.exports = postcss.plugin(plugin, (options = {}) => css => {
+const getMessages = aliases =>
+  Object.keys(aliases)
+    .map(name => ({ plugin, type: "icss-scoped", name, value: aliases[name] }))
+    .reduce((acc, msg) => [...acc, msg], []);
+
+module.exports = postcss.plugin(plugin, (options = {}) => (css, result) => {
   const generateScopedName =
     options.generateScopedName ||
     genericNames("[name]__[local]---[hash:base64:5]");
   const input = (css && css.source && css.source.input) || {};
   const aliases = {};
-  const getAlias = name => {
-    const alias = generateScopedName(name, input.from, input.css);
-    aliases[name] = alias;
-    return alias;
-  };
   walkRules(css, rule => {
+    const getAlias = name => {
+      if (aliases[name]) {
+        return aliases[name];
+      }
+      // icss-value contract
+      if (
+        result.messages.find(
+          msg => msg.type === "icss-value" && msg.value === name
+        )
+      ) {
+        return name;
+      }
+      const alias = generateScopedName(name, input.from, input.css);
+      // icss-scoped contract
+      if (
+        result.messages.find(
+          msg => msg.type === "icss-scoped" && msg.name === name
+        )
+      ) {
+        result.warn(`'${name}' already declared`, { node: rule });
+      }
+      aliases[name] = alias;
+      return alias;
+    };
     try {
       rule.selector = localizeSelectors(
         rule.selector,
@@ -139,5 +163,14 @@ module.exports = postcss.plugin(plugin, (options = {}) => css => {
       throw rule.error(e.message);
     }
   });
-  addExports(css, aliases);
+  // icss-composed contract
+  const composedAliases = Object.keys(aliases).reduce((acc, name) => {
+    const composedMsg = result.messages.find(
+      msg => msg.type === "icss-composed" && msg.name === name
+    );
+    acc[name] = aliases[name] + (composedMsg ? ` ${composedMsg.value}` : "");
+    return acc;
+  }, {});
+  result.messages.push(...getMessages(aliases));
+  addExports(css, composedAliases);
 });

test/test.js

@@ -3,15 +3,14 @@ import postcss from "postcss";
 import stripIndent from "strip-indent";
 import plugin from "../src";
 
-const strip = input =>
-  stripIndent(input).replace(/^\n/, "").replace(/\s+$/, "");
+const strip = input => stripIndent(input).trim();
 const compile = (input, options) =>
   postcss([plugin(options)])
     .process(input, options)
     .catch(e => Promise.reject(e.message));
 const generateScopedName = name => `__scope__${name}`;
-const messagesPlugin = messages => () => (css, result) => {
-  result.push(...messages);
+const messagesPlugin = messages => (css, result) => {
+  result.messages.push(...messages);
 };
 
 const runCSS = ({ fixture, expected, options }) => {
@@ -29,14 +28,25 @@ const runError = ({ fixture, error, options }) => {
   );
 };
 
-const runMessages = ({ fixture, inputMessages, outputMessages, expected }) => {
+const runMessages = ({
+  fixture,
+  inputMessages = [],
+  outputMessages,
+  warnings = [],
+  expected
+}) => {
   const processor = postcss([
     messagesPlugin(inputMessages),
     plugin({ generateScopedName })
   ]).process(strip(fixture));
   return processor.then(result => {
-    expect(result.messages).toEqual(outputMessages);
-    expect(result.css).toEqual(strip(expected));
+    expect(result.messages.filter(msg => msg.type !== "warning")).toEqual(
+      outputMessages
+    );
+    expect(result.warnings().map(msg => msg.text)).toEqual(warnings);
+    if (expected) {
+      expect(result.css).toEqual(strip(expected));
+    }
   });
 };
 
@@ -718,6 +728,7 @@ test("icss-scoped contract", () => {
       }
       .foo {}
       .bar {}
+      .foo {}
     `,
     expected: `
       :export {
@@ -726,14 +737,11 @@ test("icss-scoped contract", () => {
       }
       .__scope__foo {}
       .__scope__bar {}
+      .__scope__foo {}
     `,
+    inputMessages,
     outputMessages: [
       ...inputMessages,
-      {
-        plugin: "postcss-icss-selectors",
-        type: "warning",
-        text: `'foo' already declared by 'previous-plugin'`
-      },
       {
         plugin: "postcss-icss-selectors",
         type: "icss-scoped",
@@ -746,7 +754,8 @@ test("icss-scoped contract", () => {
         name: "bar",
         value: "__scope__bar"
       }
-    ]
+    ],
+    warnings: [`'foo' already declared`]
   });
 });
 
@@ -778,8 +787,8 @@ test("icss-composed contract", () => {
     expected: `
       :export {
         foo: __scope__foo __compose__foo;
-        bar: __scope__bar __compose__bar;
-        baz: __scope__baz
+        baz: __scope__baz;
+        bar: __scope__bar __compose__bar
       }
       .__scope__foo {}
       .__scope__bar {}