1 files changed, 25 insertions, 4 deletions
diff --git a/packages/abi-gen/src/index.ts b/packages/abi-gen/src/index.ts
index 47f2c404b..f38a162aa 100644
--- a/packages/abi-gen/src/index.ts
+++ b/packages/abi-gen/src/index.ts
@@ -8,7 +8,6 @@ import { sync as globSync } from 'glob';
 import * as Handlebars from 'handlebars';
 import * as _ from 'lodash';
 import * as mkdirp from 'mkdirp';
-import * as rimraf from 'rimraf';
 import * as yargs from 'yargs';
 
 import toSnakeCase = require('to-snake-case');
@@ -71,16 +70,34 @@ function registerPartials(partialsGlob: string): void {
     }
 }
 
-function writeOutputFile(name: string, renderedTsCode: string): void {
+function makeOutputFilePath(name: string): string {
     let fileName = toSnakeCase(name);
     // HACK: Snake case doesn't make a lot of sense for abbreviated names but we can't reliably detect abbreviations
     // so we special-case the abbreviations we use.
     fileName = fileName.replace('z_r_x', 'zrx').replace('e_r_c', 'erc');
-    const filePath = `${args.output}/${fileName}.ts`;
+    return `${args.output}/${fileName}.ts`;
+}
+
+function writeOutputFile(name: string, renderedTsCode: string): void {
+    const filePath = makeOutputFilePath(name);
     fs.writeFileSync(filePath, renderedTsCode);
     logUtils.log(`Created: ${chalk.bold(filePath)}`);
 }
 
+function isOutputFileUpToDate(abiFile: string, outFile: string): boolean {
+    const abiFileModTimeMs = fs.statSync(abiFile).mtimeMs;
+    try {
+        const outFileModTimeMs = fs.statSync(makeOutputFilePath(outFile)).mtimeMs;
+        return outFileModTimeMs > abiFileModTimeMs;
+    } catch (err) {
+        if (err.code === 'ENOENT') {
+            return false;
+        } else {
+            throw err;
+        }
+    }
+}
+
 Handlebars.registerHelper('parameterType', utils.solTypeToTsType.bind(utils, ParamKind.Input, args.backend));
 Handlebars.registerHelper('returnType', utils.solTypeToTsType.bind(utils, ParamKind.Output, args.backend));
 if (args.partials) {
@@ -97,7 +114,6 @@ if (_.isEmpty(abiFileNames)) {
     process.exit(1);
 } else {
     logUtils.log(`Found ${chalk.green(`${abiFileNames.length}`)} ${chalk.bold('ABI')} files`);
-    rimraf.sync(args.output);
     mkdirp.sync(args.output);
 }
 for (const abiFileName of abiFileNames) {
@@ -120,6 +136,11 @@ for (const abiFileName of abiFileNames) {
         process.exit(1);
     }
 
+    if (isOutputFileUpToDate(abiFileName, namedContent.name)) {
+        logUtils.log(`Already up to date: ${chalk.bold(makeOutputFilePath(namedContent.name))}`);
+        continue;
+    }
+
     let ctor = ABI.find((abi: AbiDefinition) => abi.type === ABI_TYPE_CONSTRUCTOR) as ConstructorAbi;
     if (_.isUndefined(ctor)) {
         ctor = utils.getEmptyConstructor(); // The constructor exists, but it's implicit in JSON's ABI definition