Sort files when creating the solc input

.changeset/mean-mice-tell.md

@@ -0,0 +1,5 @@
+---
+"hardhat": patch
+---
+
+Fixed an issue that was causing build-info file names to not be deterministic.

packages/hardhat-core/src/internal/solidity/compiler/compiler-input.ts

@@ -4,7 +4,13 @@ export function getInputFromCompilationJob(
   compilationJob: CompilationJob
 ): CompilerInput {
   const sources: { [sourceName: string]: { content: string } } = {};
-  for (const file of compilationJob.getResolvedFiles()) {
+
+  // we sort the files so that we always get the same compilation input
+  const resolvedFiles = compilationJob
+    .getResolvedFiles()
+    .sort((a, b) => a.sourceName.localeCompare(b.sourceName));
+
+  for (const file of resolvedFiles) {
     sources[file.sourceName] = {
       content: file.content.rawContent,
     };

packages/hardhat-core/test/builtin-tasks/compile.ts

@@ -1,4 +1,5 @@
 import { assert } from "chai";
+import ci from "ci-info";
 import * as fsExtra from "fs-extra";
 import * as path from "path";
 
@@ -817,4 +818,30 @@ Read about compiler configuration at https://hardhat.org/config
       });
     });
   });
+
+  describe("project where two contracts import the same dependency", function () {
+    useFixtureProject("consistent-build-info-names");
+    useEnvironment();
+
+    it("should always produce the same build-info name", async function () {
+      await this.env.run("compile");
+
+      const buildInfos = getBuildInfos();
+      assert.lengthOf(buildInfos, 1);
+
+      const expectedBuildInfoName = buildInfos[0];
+
+      const runs = ci.isCI ? 10 : 100;
+
+      for (let i = 0; i < runs; i++) {
+        await this.env.run("clean");
+        await this.env.run("compile");
+
+        const newBuildInfos = getBuildInfos();
+        assert.lengthOf(newBuildInfos, 1);
+
+        assert.equal(newBuildInfos[0], expectedBuildInfoName);
+      }
+    });
+  });
 });

packages/hardhat-core/test/fixture-projects/consistent-build-info-names/.gitignore

@@ -0,0 +1,2 @@
+artifacts/
+cache/

packages/hardhat-core/test/fixture-projects/consistent-build-info-names/contracts/A.sol

@@ -0,0 +1,6 @@
+pragma solidity ^0.7.0;
+
+import "dependency/contracts/Dep1.sol";
+import "dependency/contracts/Dep2.sol";
+
+contract A {}

packages/hardhat-core/test/fixture-projects/consistent-build-info-names/contracts/B.sol

@@ -0,0 +1,5 @@
+pragma solidity ^0.7.0;
+
+import "dependency/contracts/Dep1.sol";
+
+contract B {}

packages/hardhat-core/test/fixture-projects/consistent-build-info-names/hardhat.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  solidity: "0.7.3",
+};