chore: migrate generators to goog.module

[rachel-fenichel]

The basics

• I branched from develop
• My pull request is against develop
• My code follows the style guide

The details

Resolves

Proposed Changes

Behavior Before Change

Behavior After Change

Reason for Changes

Test Coverage

Documentation

Additional Information

For Javascript generators I did one commit per file. After that I switched to one commit per language.
Mocha and generator tests pass, but node tests fail--debugging that is the next step.

[cpcallen]

OK, this Closure Compiler once again kicking us because it doesn't like us renaming things in blockly.js, combined with trying to avoid setting up proper chunked compilation.

The error is:

TypeError: Blockly.Generator.Generator is not a constructor
    at /Users/cpcallen/src/blockly/dist/javascript_compressed.js:22:205

which is:

var module$contents$Blockly$JavaScript_JavaScript=new Blockly.Generator.Generator("JavaScript");

which is what the compiler outputs in response to the following lines excerpted from generators/javascript.js:

const {Generator} = goog.require('Blockly.Generator');

// ...

/**
 * JavaScript code generator.
 * @type {!Generator}
 */
const JavaScript = new Generator('JavaScript');

// ...

exports = JavaScript;

The immediate question is: why is it trying to instantiate Blockly.Generator.Generator instead of module$exports$Blockly$Generator.Generator?

At first I thought the issue might be the require('Blockly'); line at the top of javascript.js—which should definitely go!—but removing it did not solve the problem. It seems instead that it is basically the presence of externs/generator_externs.js in the compiler input, containing:

goog.provide('Blockly');
goog.provide('Blockly.Generator');
goog.provide('Blockly.inputTypes');
goog.provide('Blockly.utils.global');
goog.provide('Blockly.utils.object');
goog.provide('Blockly.utils.string');
goog.provide('Blockly.Names');
goog.provide('Blockly.Variables');
goog.provide('Blockly.Workspace');
goog.provide('Blockly.Block');
goog.provide('Blockly.Constants.Loops');

var Blockly;

Except for the first and last lines this has become a lie: the contents of the Blockly.Generator module is not available as Blockly.Generator; instead, the Generator export from the Blockly.Generator module is available as Blockly.Generator. Great for backwards compatibility for our users, not so helpful here.

Removing the goog.provide('Blockly.Generator'); line from the externs just ends up with the build failing with:

generators/javascript.js:15:20: ERROR - [JSC_MISSING_MODULE_OR_PROVIDE] Required namespace "Blockly.Generator" never defined.
  15| const {Generator} = goog.require('Blockly.Generator');
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1 error(s), 0 warning(s)

Unless someone can find a way to tell the compiler that "module Foo.Bar has been compiled and is available via a module$exports$Foo$Bar" I think we are going to have to move to chunked compilation after all.