js: Add stats and override options (#348)

- Add `RESOLC_BIN` env variable to force use a binary compiler instead
of the wasm
- Add `--diff-stats` options to print file path 

e.g

```
~/github/redstone-oracles-monorepo main*
❯ npx @parity/resolc@latest --diff-stats \
  --base-path . \
  --include-path node_modules \
  --bin packages/evm-connector/contracts/samples/SampleWithEvents.sol
┌─────────┬──────────────────────────────────────────────────────────────────────────┬───────────────────────────────┬────────────┬────────────┬───────────┐
│ (index) │ file                                                                     │ contract                      │ polkavm    │ bin        │ diff      │
├─────────┼──────────────────────────────────────────────────────────────────────────┼───────────────────────────────┼────────────┼────────────┼───────────┤
│ 0       │ 'packages/evm-connector/contracts/core/CalldataExtractor.sol'            │ 'CalldataExtractor'           │ '4.31 kB'  │ '2.53 kB'  │ '70.12%'  │
│ 1       │ 'packages/evm-connector/contracts/core/RedstoneConstants.sol'            │ 'RedstoneConstants'           │ '0.80 kB'  │ '0.17 kB'  │ '368.18%' │
│ 2       │ 'packages/evm-connector/contracts/core/RedstoneDefaultsLib.sol'          │ 'RedstoneDefaultsLib'         │ '0.90 kB'  │ '0.31 kB'  │ '189.06%' │
│ 3       │ 'packages/evm-connector/contracts/libs/BitmapLib.sol'                    │ 'BitmapLib'                   │ '0.90 kB'  │ '0.31 kB'  │ '189.06%' │
│ 4       │ 'packages/evm-connector/contracts/libs/NumericArrayLib.sol'              │ 'NumericArrayLib'             │ '0.90 kB'  │ '0.31 kB'  │ '189.06%' │
│ 5       │ 'packages/evm-connector/contracts/libs/SignatureLib.sol'                 │ 'SignatureLib'                │ '0.90 kB'  │ '0.31 kB'  │ '189.06%' │
│ 6       │ 'packages/evm-connector/contracts/mocks/RedstoneConsumerNumericMock.sol' │ 'RedstoneConsumerNumericMock' │ '13.62 kB' │ '10.17 kB' │ '33.96%'  │
│ 7       │ 'packages/evm-connector/contracts/samples/SampleWithEvents.sol'          │ 'SampleWithEvents'            │ '29.34 kB' │ '15.60 kB' │ '88.03%'  │
└─────────┴──────────────────────────────────────────────────────────────────────────┴───────────────────────────────┴────────────┴────────────┴───────────┘
```

js/resolc/src/bin.ts

@@ -6,6 +6,7 @@ import * as os from 'os'
 import * as path from 'path'
 import * as resolc from '.'
 import { SolcInput } from '.'
+import { execSync } from 'child_process'
 
 async function main() {
   // hold on to any exception handlers that existed prior to this script running, we'll be adding them back at the end
@@ -17,11 +18,15 @@ async function main() {
 
   const program = new commander.Command()
 
-  program.name('solcjs')
+  program.name('resolcjs')
   program.version(resolc.version())
   program
     .option('--bin', 'Binary of the contracts in hex.')
     .option('--abi', 'ABI of the contracts.')
+    .option(
+      '--diff-stats',
+      'Print statistics about Resolc vs Solc compilation.'
+    )
     .option(
       '--base-path <path>',
       'Root of the project source tree. ' +
@@ -49,8 +54,20 @@ async function main() {
     outputDir?: string
     prettyJson: boolean
     basePath?: string
+    diffStats: boolean
     includePath?: string[]
   }>()
+
+  // when using --stats option, we want to run solc as well to compare outputs size
+  if (options.diffStats) {
+    const args = process.argv.filter((arg) => !arg.startsWith('--diff-stats'))
+    try {
+      execSync(`npx --yes solc@latest ${args.slice(2).join(' ')}`)
+    } catch (err) {
+      abort(`Failed to run solc: ${err}`)
+    }
+  }
+
   const files: string[] = program.args
   const destination = options.outputDir ?? '.'
 
@@ -137,7 +154,7 @@ async function main() {
 
   if (!output) {
     abort('No output from compiler')
-  } else if (output.errors) {
+  } else if (output.errors && !options.diffStats) {
     for (const error in output.errors) {
       const message = output.errors[error]
       if (message.severity === 'warning') {
@@ -160,19 +177,41 @@ async function main() {
     })
   }
 
+  const contractStats = []
+
   for (const fileName in output.contracts) {
     for (const contractName in output.contracts[fileName]) {
       let contractFileName = fileName + ':' + contractName
       contractFileName = contractFileName.replace(/[:./\\]/g, '_')
-
-      if (options.bin) {
-        writeFile(
-          contractFileName + '.polkavm',
-          Buffer.from(
-            output.contracts[fileName][contractName].evm.bytecode.object,
-            'hex'
-          )
+      let polkavmSize = 0
+      let binSize = 0
+      if (
+        options.bin &&
+        output.contracts?.[fileName]?.[contractName]?.evm?.bytecode?.object
+      ) {
+        const pvmData = Buffer.from(
+          output.contracts[fileName][contractName].evm.bytecode.object,
+          'hex'
         )
+        writeFile(contractFileName + '.polkavm', pvmData)
+        polkavmSize = pvmData.length
+
+        const binOutPath = path.join(destination, `${contractFileName}.bin`)
+        if (fs.existsSync(binOutPath)) {
+          try {
+            binSize = fs.statSync(binOutPath).size || 0
+          } catch {}
+        }
+        contractStats.push({
+          file: fileName,
+          contract: contractName,
+          ['resolc (kB)']: Number((polkavmSize / 1024).toFixed(2)),
+          ['solc (kB)']: Number((binSize / 1024).toFixed(2)),
+          ['diff (%)']:
+            binSize > 0
+              ? Number(((polkavmSize / binSize - 1) * 100).toFixed(2))
+              : Number.NaN,
+        })
       }
 
       if (options.abi) {
@@ -184,6 +223,12 @@ async function main() {
     }
   }
 
+  if (options.diffStats && contractStats.length > 0) {
+    console.table(
+      contractStats.sort((a, b) => b['resolc (kB)'] - a['resolc (kB)'])
+    )
+  }
+
   // Put back original exception handlers.
   originalUncaughtExceptionListeners.forEach(function (listener) {
     process.addListener('uncaughtException', listener)

js/resolc/src/index.ts

@@ -50,11 +50,7 @@ export function resolveInputs(sources: SolcInput): SolcInput {
     language: 'Solidity',
     sources,
     settings: {
-      outputSelection: {
-        '*': {
-          '*': ['evm.bytecode.object'],
-        },
-      },
+      outputSelection: {}, // no outputs requested, only resolves imports
     },
   }
 
@@ -106,7 +102,7 @@ export async function compile(
       enabled: true,
       runs: 200,
     },
-    bin,
+    bin = process.env.RESOLC_BIN,
   } = option
 
   const input = JSON.stringify({