feat(project): Inherit configuration with yargs-like "extends"

Fixes #1281

core/project/__fixtures__/extends-circular/base.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./circular.json",
+  "loglevel": "warn"
+}

core/project/__fixtures__/extends-circular/circular.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./base.json",
+  "loglevel": "error"
+}

core/project/__fixtures__/extends-circular/lerna.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./circular.json",
+  "version": "1.0.0"
+}

core/project/__fixtures__/extends-recursive/base.json

@@ -0,0 +1,11 @@
+{
+  "packages": [
+    "base-pkgs/*"
+  ],
+  "command": {
+    "list": {
+      "json": true
+    }
+  },
+  "version": "ignored"
+}

core/project/__fixtures__/extends-recursive/lerna.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./recursive.json",
+  "version": "1.0.0"
+}

core/project/__fixtures__/extends-recursive/recursive.json

@@ -0,0 +1,11 @@
+{
+  "extends": "./base.json",
+  "packages": [
+    "recursive-pkgs/*"
+  ],
+  "command": {
+    "list": {
+      "private": false
+    }
+  }
+}

core/project/__fixtures__/extends-unresolved/lerna.json

@@ -0,0 +1,4 @@
+{
+  "extends": "unresolved",
+  "version": "1.0.0"
+}

core/project/__fixtures__/extends/lerna.json

@@ -0,0 +1,4 @@
+{
+  "extends": "local-package",
+  "version": "1.0.0"
+}

core/project/__fixtures__/extends/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "extends",
+  "version": "0.0.0-root",
+  "private": true,
+  "devDependencies": {
+    "local-package": "2.0.0"
+  }
+}

core/project/__fixtures__/pkg-prop/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "pkg-prop",
+  "version": "0.0.0-root",
+  "private": true,
+  "lerna": {
+    "loglevel": "success",
+    "command": {
+      "publish": {
+        "loglevel": "verbose"
+      }
+    },
+    "version": "1.0.0"
+  }
+}

core/project/__tests__/project.test.js

@@ -66,10 +66,9 @@ describe("Project", () => {
     });
 
     it("defaults to an empty object", async () => {
-      const cwd = await initFixture("no-lerna-config");
-      const repo = new Project(cwd);
+      await initFixture("no-lerna-config");
 
-      expect(repo.config).toEqual({});
+      expect(new Project().config).toEqual({});
     });
 
     it("errors when lerna.json is not valid JSON", async () => {
@@ -84,6 +83,91 @@ describe("Project", () => {
         expect(err.prefix).toBe("JSONError");
       }
     });
+
+    it("returns parsed rootPkg.lerna", async () => {
+      const cwd = await initFixture("pkg-prop");
+      const project = new Project(cwd);
+
+      expect(project.config).toEqual({
+        command: {
+          publish: {
+            loglevel: "verbose",
+          },
+        },
+        loglevel: "success",
+        version: "1.0.0",
+      });
+    });
+
+    it("extends local shared config", async () => {
+      const cwd = await initFixture("extends");
+      const project = new Project(cwd);
+
+      expect(project.config).toEqual({
+        packages: ["custom-local/*"],
+        version: "1.0.0",
+      });
+    });
+
+    it("extends local shared config subpath", async () => {
+      const cwd = await initFixture("extends");
+
+      await fs.writeJSON(path.resolve(cwd, "lerna.json"), {
+        extends: "local-package/subpath",
+        version: "1.0.0",
+      });
+
+      const project = new Project(cwd);
+
+      expect(project.config).toEqual({
+        packages: ["subpath-local/*"],
+        version: "1.0.0",
+      });
+    });
+
+    it("extends config recursively", async () => {
+      const cwd = await initFixture("extends-recursive");
+      const project = new Project(cwd);
+
+      expect(project.config).toEqual({
+        command: {
+          list: {
+            json: true,
+            private: false,
+          },
+        },
+        packages: ["recursive-pkgs/*"],
+        version: "1.0.0",
+      });
+    });
+
+    it("throws an error when extend target is unresolvable", async () => {
+      const cwd = await initFixture("extends-unresolved");
+
+      try {
+        // eslint-disable-next-line no-unused-vars
+        const project = new Project(cwd);
+        console.log(project);
+      } catch (err) {
+        expect(err.message).toMatch("must be locally-resolvable");
+      }
+
+      expect.assertions(1);
+    });
+
+    it("throws an error when extend target is circular", async () => {
+      const cwd = await initFixture("extends-circular");
+
+      try {
+        // eslint-disable-next-line no-unused-vars
+        const project = new Project(cwd);
+        console.log(project);
+      } catch (err) {
+        expect(err.message).toMatch("cannot be circular");
+      }
+
+      expect.assertions(1);
+    });
   });
 
   describe("get .version", () => {

core/project/index.js

@@ -10,6 +10,7 @@ const writeJsonFile = require("write-json-file");
 
 const ValidationError = require("@lerna/validation-error");
 const Package = require("@lerna/package");
+const applyExtends = require("./lib/apply-extends");
 
 class Project {
   constructor(cwd) {
@@ -36,6 +37,8 @@ class Project {
           delete obj.config.commands;
         }
 
+        obj.config = applyExtends(obj.config, path.dirname(obj.filepath));
+
         return obj;
       },
     });

core/project/lib/apply-extends.js

@@ -0,0 +1,36 @@
+"use strict";
+
+const path = require("path");
+const resolveFrom = require("resolve-from");
+const ValidationError = require("@lerna/validation-error");
+const shallowExtend = require("./shallow-extend");
+
+module.exports = applyExtends;
+
+function applyExtends(config, cwd, seen = new Set()) {
+  let defaultConfig = {};
+
+  if ("extends" in config) {
+    let pathToDefault;
+
+    try {
+      pathToDefault = resolveFrom(cwd, config.extends);
+    } catch (err) {
+      throw new ValidationError("ERESOLVED", "Config .extends must be locally-resolvable", err);
+    }
+
+    if (seen.has(pathToDefault)) {
+      throw new ValidationError("ECIRCULAR", "Config .extends cannot be circular", seen);
+    }
+
+    seen.add(pathToDefault);
+
+    // eslint-disable-next-line import/no-dynamic-require, global-require
+    defaultConfig = require(pathToDefault);
+    delete config.extends; // eslint-disable-line no-param-reassign
+
+    defaultConfig = applyExtends(defaultConfig, path.dirname(pathToDefault), seen);
+  }
+
+  return shallowExtend(config, defaultConfig);
+}

core/project/lib/shallow-extend.js

@@ -0,0 +1,20 @@
+"use strict";
+
+module.exports = shallowExtend;
+
+function shallowExtend(json, defaults = {}) {
+  return Object.keys(json).reduce((obj, key) => {
+    const val = json[key];
+
+    if (Array.isArray(val)) {
+      // always clobber arrays, merging isn't worth unexpected complexity
+      obj[key] = val.slice();
+    } else if (val && typeof val === "object") {
+      obj[key] = shallowExtend(val, obj[key]);
+    } else {
+      obj[key] = val;
+    }
+
+    return obj;
+  }, defaults);
+}

core/project/package.json

@@ -13,7 +13,8 @@
     "url": "https://github.com/evocateur"
   },
   "files": [
-    "index.js"
+    "index.js",
+    "lib"
   ],
   "main": "index.js",
   "engines": {
@@ -37,6 +38,7 @@
     "glob-parent": "^3.1.0",
     "load-json-file": "^4.0.0",
     "npmlog": "^4.1.2",
+    "resolve-from": "^4.0.0",
     "write-json-file": "^2.3.0"
   }
 }