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Feature discussion

Watchable.unwatch()

unwatch(prop, onUpdate) {
    let i = (watchers[prop] || []).findIndex(f => f === onUpdate);
    if (i === -1) {
        throw new Error();
    }
    watchers.splice(i, 1);
}

Data binding

Sophisticated user listing:

<p data-title="joinText list.authors ', ' map 'name'">
    <span class="fa fa-pencil"></span>
    <span data-content="join list.authors 'user' ', ' 3">
        <template><micro-user></micro-user></template>
        <template data-name="overflow">
            + <span data-content="sub list.authors.length 3"></span>
        </template>
    </span>
</p>

Switch:

<span data-content="switch user.role 'user' 'staff'">
    <template><button>User action</button></template>
    <template><button>Staff action</button></template>
    <template>Nothing to do</template>
</span>

<span data-content="switch user.staff true">
    <template><button>Staff action</button></template>
</span>

Format:

<span data-content="format 'Hello {user}!' 'user' user.name">
<span data-content="format 'Hello {user}!'">
    <template name="user"><micro-user data-user="user"></micro-user></template>
</span>

Translate (calls format):

<span data-content="translate 'hello' 'user' user.name">

Advanced translation example:

<p>
    <span data-content="translateEditedBy list.authors">
        <template data-name="authors">
            <span data-content="join list.authors 'user' ', ' 3">
                <template><micro-user></micro-user></template>
            </span>
        </template>
    </span>
</p>
<script>
    this.data.translateEditedBy = (ctx, authors) => {
        let n = authors.length;
        return micro.bind.translate(ctx, n > 3 ? "edited-by-overflow" : "edited-by", "n", n);
    }
    {
        "edited-by": "edited by {authors}",
        "edited-by-overflow": ["edited by {authors} and {n} other", "edited by {authors} and {n} others"]
    }
</script>

Update strategies

• Python / JavaScript API:
  • Breaking changes okay
  • User decides update time
  • Sometimes non-breaking changes are not possible or only with disproportionate effort:
    • (JavaScript) Convert <custom-element> from/to <div is="custom-element"> (can only be registered once)
• Web API:
  • Breaking changes only after deprecation period
  • Service provider decides update time, user needs time to make adjustments

Idea for non-breaking update path for function signatures:

def foo(a, b):
    # ...
# ->
def foo(a, x, b=None, __version__=1):
    if __version__ == 1:
        b, x = x, 'default'
    else:
        if b is None:
            raise Error()
    # ...
# ->
def foo(a, x, b, __version__=2):
    # ...

New features and API stability

Assume that micro introduces a new announcement feature with the following API:

• type Announcement
• Attribute Application.announcements
• DB key announcements
• endpoint /api/announcements
• page /announcements
• ...

If an existing micro application already makes use of any of those names, this could lead to breaking behavior (e.g. micro code modifies Application.announcements or posts to /api/announcements and they have different, unexpected semantics).

How can we solve this? New features that involve the extendable API could be major releases. New features could be introduced behind a feature toggle with a minor release and enabled by default with a major release. DB keys could be prefixed with micro.

Linting

Rules that may be worth considering:

• multiline-comment-style (ESLint 4.9)