Add dependency message support

index.js

@@ -218,7 +218,11 @@ function resolveImportId(
   state
 ) {
   var atRule = stmt.node
-  var base = atRule.source && atRule.source.input && atRule.source.input.file
+  var sourceFile
+  if (atRule.source && atRule.source.input && atRule.source.input.file) {
+    sourceFile = atRule.source.input.file
+  }
+  var base = sourceFile
     ? path.dirname(atRule.source.input.file)
     : options.root
 
@@ -227,6 +231,16 @@ function resolveImportId(
     if (!Array.isArray(resolved)) {
       resolved = [ resolved ]
     }
+
+    // Add dependency messages:
+    resolved.forEach(function(file) {
+      result.messages.push({
+        type: "dependency",
+        file: file,
+        parent: sourceFile,
+      })
+    })
+
     return Promise.all(resolved.map(function(file) {
       return loadImportContent(
         result,

test/callback.js → test/import-events.js

@@ -52,3 +52,31 @@ test("should have a callback shortcut for webpack", t => {
       )
     })
 })
+
+test("should add dependency message for each import", t => {
+  return postcss()
+    .use(atImport({
+      path: "fixtures/imports",
+    }))
+    .process(readFileSync("fixtures/media-import.css"), {
+      from: "fixtures/media-import.css",
+    })
+    .then((result) => {
+      var deps = result.messages.filter(
+        message => message.type === "dependency"
+      )
+      var expected = [
+        {
+          type: "dependency",
+          file: resolve("fixtures/imports/media-import-level-2.css"),
+          parent: resolve("fixtures/media-import.css"),
+        },
+        {
+          type: "dependency",
+          file: resolve("fixtures/imports/media-import-level-3.css"),
+          parent: resolve("fixtures/imports/media-import-level-2.css"),
+        },
+      ]
+      t.deepEqual(deps, expected)
+    })
+})