core: add default audit options with scoring

[patrickhulce]

closes #4873

[brendankenny]

would it be better to leave the default in the file and allow overriding instead?

[patrickhulce]

would it be better to leave the default in the file and allow overriding instead?

I thought about that, but for our magic --print-config I'm looking forward to you implementing, this seemed better ;)

[paulirish]

@patrickhulce wdyt about using defaultOptions which come along with the audit. it delivers its own so you don't need the config to describe how exactly each audit gets used.

e.g. https://github.com/paulirish/pwmetrics/blob/master/lib/lh-config.ts doesn't need to reference the constants just to provide defaults.

the basic pattern we're thinking of:

diff --git a/lighthouse-core/audits/audit.js b/lighthouse-core/audits/audit.js
index 227868c9..4bd800a7 100644
--- a/lighthouse-core/audits/audit.js
+++ b/lighthouse-core/audits/audit.js
@@ -42,6 +42,10 @@ class Audit {
     throw new Error('Audit meta information must be overridden.');
   }
 
+  static get defaultOptions() {
+    return {};
+  }
+
   /**
    * Computes a clamped score between 0 and 1 based on the measured value. Score is determined by
    * considering a log-normal distribution governed by the two control points, point of diminishing
diff --git a/lighthouse-core/audits/first-meaningful-paint.js b/lighthouse-core/audits/first-meaningful-paint.js
index 78273bdd..ae2e4d1d 100644
--- a/lighthouse-core/audits/first-meaningful-paint.js
+++ b/lighthouse-core/audits/first-meaningful-paint.js
@@ -24,6 +24,13 @@ class FirstMeaningfulPaint extends Audit {
     };
   }
 
+  static get defaultOptions() {
+    return {
+      scorePODR: 1600,
+      scoreMedian: 4000,
+    };
+  }
+
   /**
    * Audits the page to give a score for First Meaningful Paint.
    * @see https://github.com/GoogleChrome/lighthouse/issues/26
diff --git a/lighthouse-core/config/default-config.js b/lighthouse-core/config/default-config.js
index 33fd498b..70bc63e0 100644
--- a/lighthouse-core/config/default-config.js
+++ b/lighthouse-core/config/default-config.js
@@ -75,7 +75,7 @@ module.exports = {
     'works-offline',
     'viewport',
     'without-javascript',
-    {path: 'first-meaningful-paint', options: auditOptions['first-meaningful-paint']},
+    {path: 'first-meaningful-paint'},
     'load-fast-enough-for-pwa',
     {path: 'speed-index-metric', options: auditOptions['speed-index-metric']},
     'screenshot-thumbnails',
diff --git a/lighthouse-core/runner.js b/lighthouse-core/runner.js
index 65cdfb76..5b77f475 100644
--- a/lighthouse-core/runner.js
+++ b/lighthouse-core/runner.js
@@ -260,8 +260,9 @@ class Runner {
           throw error;
         }
       }
+      const options = {...audit.defaultOptions, ...(auditDefn.options || {})};
       // all required artifacts are in good shape, so we proceed
-      return audit.audit(artifacts, {options: auditDefn.options || {}, settings: opts.settings});
+      return audit.audit(artifacts, {options, settings: opts.settings});
     // Fill remaining audit result fields.
     }).then(auditResult => Audit.generateAuditResult(audit, auditResult))
     .catch(err => {

[patrickhulce]

aight, defaultOptions here we are! this what you had in mind @paulirish ?

[brendankenny]

LGTM! Thanks for dealing with the dumb churn :)

[brendankenny]

do we want to preserve these to save a click? @paulirish used to like these especially

[patrickhulce]

IMO they've limited value in their current form since they're inconsistently documenting percentiles and near the context.options rather than the defaultOptions declaration. I'd prefer to stick to the graphs and get better at interpreting the PODR and median.

alternatively I had an idea that we express the score in terms of the green/yellow transition and yellow/red transition and the function just finds the curve that fits (yellow/red is already median) but I def don't want to make that change in this PR :)

[brendankenny]

agreed on inconsistent across files and yeah, they would need to move to live near defaultOptions (they could live in the jsdoc, for instance).

I don't feel particularly strongly about them, but I do see the appeal of not having to click through and hover over the graph to get a sense of scoring.

On the other other hand, this kind of thing should likely live in the docs (and mayyyyybe the report?) anyways :)

[paulirish]

Let's nuke