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Making progress on async

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Tim Hardy
2016-09-22 08:47:09 -05:00
parent dc85c80afe
commit 87e284159d
4 changed files with 171 additions and 63 deletions
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src/render.js
+99 -25
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@@ -7,32 +7,106 @@ var render = {
renderTemplates: function(templates, scope) {
assert(scope, 'unable to evalTemplates: scope undefined');
var htmlBlocks = [],
partial,
promises = [];
templates.some((template, index) => {
if (scope.get('forloop.skip')) return true;
switch (template.type) {
case 'tag':
promises.push(this.renderTag(template, scope, this.register)
.then((partial) => {
if (partial === undefined) return true;
return htmlBlocks[index] = partial;
}));
break;
case 'html':
promises.push(Promise.resolve(htmlBlocks[index] = template.value));
break;
case 'output':
var val = this.evalOutput(template, scope);
htmlBlocks[index] = val === undefined ? '' : stringify(val);
promises.push(Promise.resolve(htmlBlocks[index]));
}
});
return Promise.all(promises)
.then((results) => {
return htmlBlocks.join('');
var html = '';
// var promiseChain = Promise.resolve(''); // create an empty promise to begin the chain;
// templates.some((template, index) => {
// if (scope.get('forloop.skip')) return true;
// var promiseLink = Promise.resolve('');
// switch (template.type) {
// case 'tag':
// // Add Promises to the chain that need to be resolved sequentially
// promiseLink = this.renderTag(template, scope, this.register)
// .then((partial) => {
// if (partial === undefined) return true; // basically a noop (do nothing)
// html += partial;
// });
// promiseChain = promiseChain.then(promiseLink); // add a link to the chain
// break;
// case 'html':
// promiseLink = Promise.resolve(template.value)
// .then((partial) => {
// html += partial;
// });
// promiseChain = promiseChain.then(promiseLink); // add a link to the chain
// break;
// case 'output':
// var val = this.evalOutput(template, scope);
// promiseLink = Promise.resolve(val === undefined ? '' : stringify(val))
// .then((partial) => {
// html += partial;
// });
// promiseChain = promiseChain.then(promiseLink); // add a link to the chain
// }
// });
// return promiseChain.then((result) => {
// // this should happen after all of the above promises are finished, and they should have resolved in order
// return html;
// });
// This executes an array of promises sequentially for every template in the templates array - http://webcache.googleusercontent.com/search?q=cache:rNbMUn9TPtkJ:joost.vunderink.net/blog/2014/12/15/processing-an-array-of-promises-sequentially-in-node-js/+&cd=5&hl=en&ct=clnk&gl=us
// It's fundamentally equivalent to the following...
// emptyPromise.then(renderTag(template0).then(renderTag(template1).then(renderTag(template2)...
var lastPromise = templates.reduce((promise, template) => {
return promise.then((partial) => {
if (scope.get('forloop.skip')) {
return Promise.resolve('');
}
if (scope.get('forloop.stop')) {
throw new Error('forloop.stop'); // this will stop/break the sequential promise chain and go to the catch
}
var promiseLink = Promise.resolve('');
switch (template.type) {
case 'tag':
// Add Promises to the chain
promiseLink = this.renderTag(template, scope, this.register)
.then((partial) => {
if (partial === undefined) {
return true; // basically a noop (do nothing)
}
return html += partial;
});
break;
case 'html':
promiseLink = Promise.resolve(template.value)
.then((partial) => {
return html += partial;
});
break;
case 'output':
var val = this.evalOutput(template, scope);
promiseLink = Promise.resolve(val === undefined ? '' : stringify(val))
.then((partial) => {
return html += partial;
});
break;
}
return promiseLink;
})
.catch((error) => {
if (error === 'forloop.stop') {
// the error is a controlled, purposeful stop. so just return the html that we have up to this point
return html;
} else {
// rethrow actual error
throw new Error(error);
}
});
}, Promise.resolve('')); // start the reduce chain with a resolved Promise. After first run, the "promise" argument
// in our reduce callback will be the returned promise from our "then" above. In this
// case, that's the promise returned from this.renderTag or a resolved promise with raw html.
return lastPromise
.then(() => {
return html;
})
.catch((error) => {
throw new Error(error);
});
},
renderTag: function(template, scope, register) {