Thanks for Pull Request!

Is gitbook-plugin-changelog https://github.com/antonlegoo/gitbook-plugin-changelog?
I can not found <img> task on gitbook-plugin-changelog?
The <img src="...."> come from your commit message?

Mine understand that

commit message → gitbook-plugin-changelog → HonKit's resolveImages (bug) → invalid result

I think that src value is .... of your example. (not undefined and not null).
Does This fix work it correctly?

Also, Can you add test for resolveImages like resolveLinks.js?

@azu

The come from your commit message?

Yes, that's right.

When img tag has break return and src is started with line head, in the git diff, src is started with plus sign like this.

+<img
+src="...">

In this case, resolveImages can find img tag but cannot find src..
I confirmed this change fixes my case, but sorry, I didn't confirm src is whether null or undefined in this case.

But if src is null or undefined, the following line must be error.

src = LocationUtils.toAbsolute(src, currentDirectory, ".");

LocationUtils.toAbsolute calls toAbsorute and it calls normalize in location.js, this function expect string as argument.

So, I think resolveImages should check src is whether string or not.

@azu ah, I haven't detected which is real problem whether src with plus sign is problem or img tag with break line is problem

@azu I'll write test later, but it'll take a few days.

Also, Can you add test for resolveImages like resolveLinks.js?

In this case, resolveImages can find img tag but cannot find src..

Ah, I see.

This PR is reasonable to fix <img /> handling.

@azu ah, I haven't detected which is real problem whether src with plus sign is problem or img tag with break line is problem

Me too.
I expect that HonKit uses old version of cheerio and this bug come from old version cheerio, maybe.

In html, following img tag is valid syntax.

<img
src=x
>

@azu I'll write test later, but it'll take a few days.

Yes!

@azu I add new test.

I confirmed the test is aborted on master branch.

FAIL src/output/modifiers/__tests__/resolveImages.js
  ● resolveLinks › img tag with src with plus sign › no error occurs and return undefined

    TypeError: The "path" argument must be of type string. Received undefinedTypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined

      37 | // Normalize a path to be a link
      38 | function normalize(s) {
    > 39 |     return path.normalize(s).replace(/\\/g, "/");
         |                 ^
      40 | }
      41 | 
      42 | /**

      at normalize (src/utils/location.js:39:17)
      at Object.toAbsolute (src/utils/location.js:72:13)
      at src/output/modifiers/resolveImages.js:24:29
      at src/output/modifiers/editHTMLElement.js:11:16
      at src/utils/promise.js:36:16
      at src/utils/promise.js:22:20
      at _fulfilled (../../node_modules/q/q.js:854:54)
      at ../../node_modules/q/q.js:883:30

as a result, break return is no problem.
src with plus sign is problem. ex <img +src="..."> occurs error.

Relase v3.5.3

It seems that this fix is not included v3.5.3.
Something goes worng...?

The following is install log and result of grep.

npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
/home/ktat/.nodebrew/node/v14.5.0/bin/honkit -> /home/ktat/.nodebrew/node/v14.5.0/lib/node_modules/honkit/bin/honkit.js
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@~2.1.2 (node_modules/honkit/node_modules/chokidar/node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.1.3: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

+ honkit@3.5.3
updated 1 package in 3.737s
[ktat@katt:(git)master] grep src /home/ktat/.nodebrew/node/v14.5.0/lib/node_modules/honkit/lib/output/modifiers/resolveImages.js
        let src = $img.attr("src");
        if (LocationUtils.isExternal(src) || LocationUtils.isDataURI(src)) {
        src = LocationUtils.toAbsolute(src, currentDirectory, ".");
        src = LocationUtils.relative(currentDirectory, src);
        $img.attr("src", src);

@ktat Ah, Nice catch!

I've added prepublish script and re-publish it as 3.5.4
810fcc7