Fix for issue nathanhleung#43. install peer deps doesn't update a pee…

…r dep when a more recent version is already installed.

.gitignore

@@ -4,6 +4,7 @@
 
 # Fixtures ignore
 fixtures/sandbox/node_modules/
+fixtures/has-newer-peer-dep/node_modules/
 
 ## From https://raw.githubusercontent.com/github/gitignore/master/Node.gitignore
 # Logs

fixtures/has-newer-peer-dep/README.MD

@@ -0,0 +1,8 @@
+
+Example project to illustrate [issue 43](https://github.com/nathanhleung/install-peerdeps/issues/43).
+
+This project has data-forge 1.3.3 installed.
+
+It also has data-forge-indicators 0.1.7 which has a peer dependency on data-forge 1.0.10.
+
+Previously using install-peerdeps to install peers of data-forge-indicators would have overwritten data-forge with the older version.

fixtures/has-newer-peer-dep/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "has-newer-peer-deps",
+  "private": true,
+  "dependencies": {
+    "data-forge": "1.3.3",
+    "data-forge-indicators": "0.1.7"
+  }
+}

src/cli.test.js

@@ -1,7 +1,7 @@
-import { spawn } from "child_process";
+import { spawn, exec } from "child_process";
 import path from "path";
 import test from "tape";
-// import fs from "fs";
+import fs from "fs";
 
 /**
  * Spawns the CLI with the provided arguments
@@ -52,6 +52,50 @@ async function getCliInstallCommand(extraArgs) {
   });
 }
 
+/**
+ * Run a shell command.
+ * @param {string} cmd - The command to run.
+ * @param {string} cwd - Working directory for the command.
+ */
+function runCmd(cmd, cwd) {
+  return new Promise((resolve, reject) => {
+    console.log(`! ${cmd} in ${cwd}`);
+    exec(cmd, { cwd }, (err /* , stdout, stderr */) => {
+      if (err) {
+        reject(err);
+      } else {
+        resolve();
+      }
+    });
+  });
+}
+
+/**
+ * Cleans and reinstalls modules in a fixture directory.
+ * @param {string} fixture - The fixture for which to reset node modules.
+ */
+async function resetFixtureNodeModules(fixture) {
+  const cwd = path.join(__dirname, "..", "fixtures", fixture);
+  await runCmd("rm -rf node_modules", cwd);
+  await runCmd("npm install", cwd);
+}
+
+/**
+ * Read a JSON file from disk.
+ * @param {string} filePath - The path to the JSON file to be read.
+ */
+function readJSON(filePath) {
+  return new Promise((resolve, reject) => {
+    fs.readFile(filePath, "utf8", (err, packageFileJson) => {
+      if (err) {
+        reject(err);
+      } else {
+        resolve(JSON.parse(packageFileJson));
+      }
+    });
+  });
+}
+
 test("errors when more than one package is provided", t => {
   const cli = spawnCli(["eslint-config-airbnb", "angular"]);
   cli.on("exit", code => {
@@ -133,6 +177,32 @@ test("installs packages correctly even if package name ends with '-0'", t => {
   });
 });
 
+test("peer dependency is not installed when a later version already exists", t => {
+  resetFixtureNodeModules("has-newer-peer-dep")
+    .then(() => {
+      const cli = spawnCli("data-forge-indicators", "has-newer-peer-dep");
+      cli.on("exit", code => {
+        t.equal(code, 0, `errored, exit code was ${code}`);
+
+        readJSON(
+          "fixtures/has-newer-peer-dep/node_modules/data-forge/package.json"
+        )
+          .then(packageFile => {
+            t.equal(packageFile.version, "1.3.3", "Bad version!");
+            t.end();
+          })
+          .catch(err => {
+            t.fail((err && err.stack) || err);
+            t.end();
+          });
+      });
+    })
+    .catch(err => {
+      t.fail((err && err.stack) || err);
+      t.end();
+    });
+});
+
 // Work on this test later
 /*
 test("doesn't replace existing installed peer dependencies", t => {