Ability to break on `:` for objects (#314)

src/printer.js

@@ -609,7 +609,25 @@ function genericPrintNoParens(path, options, print) {
         } else {
           parts.push(printPropertyKey(path, options, print));
         }
-        parts.push(": ", path.call(print, "value"));
+
+        let printedValue = path.call(print, "value");
+        if (shouldPrintSameLine(n.value)) {
+          parts.push(concat([": ", printedValue]));
+        } else {
+          parts.push(
+            concat([
+              group(
+                concat([
+                  ":",
+                  ifBreak(" (", " "),
+                  indent(options.tabWidth, concat([softline, printedValue]))
+                ])
+              ),
+              line,
+              ifBreak(")")
+            ])
+          );
+        }
       }
 
       return concat(parts);
@@ -2458,6 +2476,26 @@ function isLastStatement(path) {
   return body && body[body.length - 1] === node;
 }
 
+function shouldPrintSameLine(node) {
+  const type = node.type;
+  return namedTypes.Literal.check(node) ||
+    type === "ArrayExpression" ||
+    type === "ArrayPattern" ||
+    type === "ArrowFunctionExpression" ||
+    type === "AssignmentPattern" ||
+    type === "CallExpression" ||
+    type === "FunctionExpression" ||
+    type === "Identifier" ||
+    type === "Literal" ||
+    type === "MemberExpression" ||
+    type === "NewExpression" ||
+    type === "ObjectExpression" ||
+    type === "ObjectPattern" ||
+    type === "StringLiteral" ||
+    type === "ThisExpression" ||
+    type === "TypeCastExpression";
+}
+
 function printAstToDoc(ast, options) {
   function printGenerically(path) {
     return comments.printComments(

tests/logical/__snapshots__/jsfmt.spec.js.snap

@@ -901,14 +901,14 @@ function logical12b(y: number): number {
  */
 function logical13(x: number): Array<{ x: string }> {
   return [
-    { x: x && \"bar\" },
-    { x: true && \"bar\" },
-    { x: true && false },
-    { x: false && false },
-    { x: 1 && \"bar\" },
-    { x: \"foo\" && \"bar\" },
-    { x: \"foo\" && \"bar\" },
-    { x: \"foo\" && \"bar\" }
+    { x: x && \"bar\"  },
+    { x: true && \"bar\"  },
+    { x: true && false  },
+    { x: false && false  },
+    { x: 1 && \"bar\"  },
+    { x: \"foo\" && \"bar\"  },
+    { x: \"foo\" && \"bar\"  },
+    { x: \"foo\" && \"bar\"  }
   ];
 }
 
@@ -917,14 +917,14 @@ function logical13(x: number): Array<{ x: string }> {
  */
 function logical14(x: number): Array<{ x: string }> {
   return [
-    { x: x || \"bar\" },
-    { x: false || \"bar\" },
-    { x: false || true },
-    { x: true || false },
-    { x: 0 || \"bar\" },
-    { x: \"foo\" || \"bar\" },
-    { x: \"foo\" || \"bar\" },
-    { x: \"foo\" || \"bar\" }
+    { x: x || \"bar\"  },
+    { x: false || \"bar\"  },
+    { x: false || true  },
+    { x: true || false  },
+    { x: 0 || \"bar\"  },
+    { x: \"foo\" || \"bar\"  },
+    { x: \"foo\" || \"bar\"  },
+    { x: \"foo\" || \"bar\"  }
   ];
 }
 

tests/prettier/__snapshots__/jsfmt.spec.js.snap

@@ -690,6 +690,71 @@ method()
 "
 `;
 
+exports[`test object-prop-break-in.js 1`] = `
+"const a = classnames({
+  \"some-prop\": this.state.longLongLongLongLongLongLongLongLongTooLongProp
+});
+
+const b = classnames({
+  \"some-prop\": this.state.longLongLongLongLongLongLongLongLongTooLongProp === true
+});
+
+const c = classnames({
+  \"some-prop\": [ \"foo\", \"bar\", \"foo\", \"bar\", \"foo\", \"bar\", \"foo\", \"bar\", \"foo\" ]
+});
+
+const d = classnames({
+  \"some-prop\": () => {}
+});
+
+const e = classnames({
+  \"some-prop\": function bar() {}
+});
+
+const f = classnames({
+  \"some-prop\": { foo: \"bar\", bar: \"foo\", foo: \"bar\", bar: \"foo\", foo: \"bar\" }
+});
+
+const g = classnames({
+  \"some-prop\": longLongLongLongLongLongLongLongLongLongLongLongLongTooLongVar || 1337
+});
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+const a = classnames({
+  \"some-prop\": this.state.longLongLongLongLongLongLongLongLongTooLongProp
+});
+
+const b = classnames({
+  \"some-prop\": (
+    this.state.longLongLongLongLongLongLongLongLongTooLongProp === true
+  )
+});
+
+const c = classnames({
+  \"some-prop\": [ \"foo\", \"bar\", \"foo\", \"bar\", \"foo\", \"bar\", \"foo\", \"bar\", \"foo\" ]
+});
+
+const d = classnames({
+  \"some-prop\": () => {
+  }
+});
+
+const e = classnames({
+  \"some-prop\": function bar() {
+  }
+});
+
+const f = classnames({
+  \"some-prop\": { foo: \"bar\", bar: \"foo\", foo: \"bar\", bar: \"foo\", foo: \"bar\" }
+});
+
+const g = classnames({
+  \"some-prop\": (
+    longLongLongLongLongLongLongLongLongLongLongLongLongTooLongVar || 1337
+  )
+});
+"
+`;
+
 exports[`test optional-type-name.js 1`] = `
 "type Foo = (any) => string
 

tests/prettier/object-prop-break-in.js

@@ -0,0 +1,27 @@
+const a = classnames({
+  "some-prop": this.state.longLongLongLongLongLongLongLongLongTooLongProp
+});
+
+const b = classnames({
+  "some-prop": this.state.longLongLongLongLongLongLongLongLongTooLongProp === true
+});
+
+const c = classnames({
+  "some-prop": [ "foo", "bar", "foo", "bar", "foo", "bar", "foo", "bar", "foo" ]
+});
+
+const d = classnames({
+  "some-prop": () => {}
+});
+
+const e = classnames({
+  "some-prop": function bar() {}
+});
+
+const f = classnames({
+  "some-prop": { foo: "bar", bar: "foo", foo: "bar", bar: "foo", foo: "bar" }
+});
+
+const g = classnames({
+  "some-prop": longLongLongLongLongLongLongLongLongLongLongLongLongTooLongVar || 1337
+});