Truffle flattener cyclic dependencies error - re-work on PR #844 (#857)

* Show a detailed error with next steps when cyclic dependencies are found

* Add error handler on contract  deployment task

* Unified truffle flattener cyclic dependency errors

* Add return and array to flatten call

packages/aragon-cli/src/commands/apm_cmds/util/generate-artifact.js

@@ -1,7 +1,7 @@
 const fs = require('fs')
 const path = require('path')
 const { readJson, writeJson } = require('fs-extra')
-const flatten = require('truffle-flattener')
+const flattenCode = require('../../../helpers/flattenCode')
 const extract = require('../../../helpers/solidity-extractor')
 const namehash = require('eth-ens-namehash')
 const taskInput = require('listr-input')
@@ -152,7 +152,7 @@ async function generateApplicationArtifact(
 }
 
 async function generateFlattenedCode(dir, sourcePath) {
-  const flattenedCode = await flatten([sourcePath])
+  const flattenedCode = await flattenCode([sourcePath])
   fs.writeFileSync(path.resolve(dir, SOLIDITY_FILE), flattenedCode)
 }
 

packages/aragon-cli/src/helpers/flattenCode.js

@@ -0,0 +1,22 @@
+const flatten = require('truffle-flattener')
+
+module.exports = async (sourcePaths) => {
+  try {
+    return flatten(sourcePaths)
+  } catch (error) {
+    const cycleDependencyErrorDetected = /cycle.+dependency/.test(error.message)
+    if (cycleDependencyErrorDetected) {
+      throw Error(`Cyclic dependencies in .sol files are not supported.
+'truffle-flattener' requires all cyclic dependencies to be resolved before proceeding.
+To do so, you can:
+- Remove unnecessary import statements, if any
+- Abstract the interface of imported contracts in a separate file
+- Merge multiple contracts in a single .sol file
+
+Original error: ${error}
+`)
+    } else {
+      throw error
+    }
+  }
+}

packages/aragon-cli/src/helpers/truffle-deploy-artifacts.js

@@ -1,4 +1,4 @@
-const flatten = require('truffle-flattener')
+const flattenCode = require('../helpers/flattenCode')
 const { getTruffleConfig } = require('./truffle-config')
 
 module.exports = async contractArtifacts => {
@@ -11,7 +11,8 @@ module.exports = async contractArtifacts => {
 
   const solcConfig = getTruffleConfig().solc
   compiler.optimizer = solcConfig ? solcConfig.optimizer : { enabled: false }
-  const flattenedCode = await flatten([sourcePath])
+
+  const flattenedCode = await flattenCode([sourcePath])
 
   return {
     contractName,