Add opts.message option to code frames (babel#7243)

* Add opts.message option to code frames

* Fix for missing loc.start in code-frame

* Add docs

packages/babel-code-frame/README.md

@@ -68,6 +68,7 @@ console.log(result);
 
 Toggles syntax highlighting the code as JavaScript for terminals.
 
+
 ### `linesAbove`
 
 `number`, defaults to `2`.
@@ -86,6 +87,21 @@ Adjust the number of lines to show below the error.
 
 Enable this to forcibly syntax highlight the code as JavaScript (for non-terminals); overrides `highlightCode`.
 
+### `message`
+
+`string`, otherwise nothing
+
+Pass in a string to be displayed inline (if possible) next to the highlighted
+location in the code. If it can't be positioned inline, it will be placed above
+the code frame.
+
+```
+1 | class Foo {
+> 2 |   constructor()
+  |                ^ Missing {
+3 | };
+```
+
 ## Upgrading from prior versions
 
 Prior to version 7, the only API exposed by this module was for a single line and optional column pointer. The old API will now log a deprecation warning.

packages/babel-code-frame/src/index.js

@@ -32,6 +32,7 @@ function getDefs(chalk) {
     invalid: chalk.white.bgRed.bold,
     gutter: chalk.grey,
     marker: chalk.red.bold,
+    message: chalk.red.bold,
   };
 }
 
@@ -200,16 +201,18 @@ export function codeFrameColumns(
 
   const lines = rawLines.split(NEWLINE);
   const { start, end, markerLines } = getMarkerLines(loc, lines, opts);
+  const hasColumns = loc.start && typeof loc.start.column === "number";
 
   const numberMaxWidth = String(end).length;
 
-  const frame = lines
+  let frame = lines
     .slice(start, end)
     .map((line, index) => {
       const number = start + 1 + index;
       const paddedNumber = ` ${number}`.slice(-numberMaxWidth);
       const gutter = ` ${paddedNumber} | `;
       const hasMarker = markerLines[number];
+      const lastMarkerLine = !markerLines[number + 1];
       if (hasMarker) {
         let markerLine = "";
         if (Array.isArray(hasMarker)) {
@@ -224,6 +227,10 @@ export function codeFrameColumns(
             markerSpacing,
             maybeHighlight(defs.marker, "^").repeat(numberOfMarkers),
           ].join("");
+
+          if (lastMarkerLine && opts.message) {
+            markerLine += " " + maybeHighlight(defs.message, opts.message);
+          }
         }
         return [
           maybeHighlight(defs.marker, ">"),
@@ -237,6 +244,10 @@ export function codeFrameColumns(
     })
     .join("\n");
 
+  if (opts.message && !hasColumns) {
+    frame = `${" ".repeat(numberMaxWidth + 1)}${opts.message}\n${frame}`;
+  }
+
   if (highlighted) {
     return chalk.reset(frame);
   } else {

packages/babel-code-frame/test/index.js

@@ -299,4 +299,101 @@ describe("@babel/code-frame", function() {
       ].join("\n"),
     );
   });
+
+  it("opts.message", function() {
+    const rawLines = ["class Foo {", "  constructor()", "};"].join("\n");
+    assert.equal(
+      codeFrameColumns(
+        rawLines,
+        { start: { line: 2, column: 16 } },
+        {
+          message: "Missing {",
+        },
+      ),
+      [
+        "  1 | class Foo {",
+        "> 2 |   constructor()",
+        "    |                ^ Missing {",
+        "  3 | };",
+      ].join("\n"),
+    );
+  });
+
+  it("opts.message without column", function() {
+    const rawLines = ["class Foo {", "  constructor()", "};"].join("\n");
+    assert.equal(
+      codeFrameColumns(
+        rawLines,
+        { start: { line: 2 } },
+        {
+          message: "Missing {",
+        },
+      ),
+      [
+        "  Missing {",
+        "  1 | class Foo {",
+        "> 2 |   constructor()",
+        "  3 | };",
+      ].join("\n"),
+    );
+  });
+
+  it("opts.message with multiple lines", function() {
+    const rawLines = [
+      "class Foo {",
+      "  constructor() {",
+      "    console.log(arguments);",
+      "  }",
+      "};",
+    ].join("\n");
+    assert.equal(
+      codeFrameColumns(
+        rawLines,
+        {
+          start: { line: 2, column: 17 },
+          end: { line: 4, column: 3 },
+        },
+        {
+          message: "something about the constructor body",
+        },
+      ),
+      [
+        "  1 | class Foo {",
+        "> 2 |   constructor() {",
+        "    |                 ^",
+        "> 3 |     console.log(arguments);",
+        "    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^",
+        "> 4 |   }",
+        "    | ^^^ something about the constructor body",
+        "  5 | };",
+      ].join("\n"),
+    );
+  });
+
+  it("opts.message with multiple lines without columns", function() {
+    const rawLines = [
+      "class Foo {",
+      "  constructor() {",
+      "    console.log(arguments);",
+      "  }",
+      "};",
+    ].join("\n");
+    assert.equal(
+      codeFrameColumns(
+        rawLines,
+        { start: { line: 2 }, end: { line: 4 } },
+        {
+          message: "something about the constructor body",
+        },
+      ),
+      [
+        "  something about the constructor body",
+        "  1 | class Foo {",
+        "> 2 |   constructor() {",
+        "> 3 |     console.log(arguments);",
+        "> 4 |   }",
+        "  5 | };",
+      ].join("\n"),
+    );
+  });
 });