From 55e5f708b431bd839b63b1910967bb90fe959c6a Mon Sep 17 00:00:00 2001
From: Kevin Gibbons <bakkot@gmail.com>
Date: Tue, 18 Aug 2020 15:08:09 -0700
Subject: [PATCH] lint: forbid leading/trailing whitespace within tags

---
 src/lint/collect-spelling-diagnostics.ts |  8 +++++++
 test/lint-spelling.js                    | 29 ++++++++++++++++++++++++
 test/lint.js                             |  4 ++--
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/lint/collect-spelling-diagnostics.ts b/src/lint/collect-spelling-diagnostics.ts
index da212124..f79dd30a 100644
--- a/src/lint/collect-spelling-diagnostics.ts
+++ b/src/lint/collect-spelling-diagnostics.ts
@@ -65,6 +65,14 @@ let matchers = [
     pattern: /(?<=\S)  +(?! |<\/(td|th|dd|dt)>)/gu,
     message: 'multiple consecutive spaces are not allowed',
   },
+  {
+    pattern: /(?<=<[a-z]+( [a-z]+(="[^"\n]+")?)*>)(?<!(td|th|dd|dt)>) /gu,
+    message: 'tags should not contain leading whitespace',
+  },
+  {
+    pattern: /(?<=[^ \n]) +<\/(?!td|th|dd|dt)/gu,
+    message: 'tags should not contain trailing whitespace',
+  },
 ];
 
 export function collectSpellingDiagnostics(
diff --git a/test/lint-spelling.js b/test/lint-spelling.js
index f647a76e..fcdf8ca7 100644
--- a/test/lint-spelling.js
+++ b/test/lint-spelling.js
@@ -211,6 +211,32 @@ windows:${M}\r
     );
   });
 
+  it('leading whitespace within tags', async function () {
+    await assertLint(
+      positioned`
+        <p>${M} This is an example.</p>
+      `,
+      {
+        ruleId: 'spelling',
+        nodeType: 'html',
+        message: 'tags should not contain leading whitespace',
+      }
+    );
+  });
+
+  it('trailing whitespace within tags', async function () {
+    await assertLint(
+      positioned`
+        <p>This is an example:${M} </p>
+      `,
+      {
+        ruleId: 'spelling',
+        nodeType: 'html',
+        message: 'tags should not contain trailing whitespace',
+      }
+    );
+  });
+
   it('negative', async function () {
     await assertLintFree(`
       <p>
@@ -241,6 +267,9 @@ windows:${M}\r
       <td> Also to pad them a bit, in some cases.                   </td>
       </tr></table>
 
+      <p>
+        Paragraphs with the open/close tags on their own line are OK.
+      </p>
     `);
   });
 });
diff --git a/test/lint.js b/test/lint.js
index fe33dbf4..b3a542bd 100644
--- a/test/lint.js
+++ b/test/lint.js
@@ -58,7 +58,7 @@ describe('linting whole program', function () {
     it('error in inline grammar', async function () {
       await assertLint(
         positioned`
-          <emu-grammar type="definition"> Statement[${M}a]: \`;\` </emu-grammar>
+          <emu-grammar type="definition">Statement[${M}a]: \`;\`</emu-grammar>
         `,
         {
           ruleId: 'grammarkdown:2008',
@@ -91,7 +91,7 @@ describe('linting whole program', function () {
     it('error in inline grammar', async function () {
       await assertLint(
         positioned`
-          <emu-grammar> ${M}Statement: EmptyStatement </emu-grammar>
+          <emu-grammar>${M}Statement: EmptyStatement</emu-grammar>
           <emu-alg>
             1. Return Foo.
           </emu-alg>