refactor: code

src/index.js

@@ -13,12 +13,10 @@ import {
   exec,
   normalizeSourceMap,
   normalizeSourceMapAfterPostcss,
-  parsePackageJson,
-  findPackageJsonDir,
+  findPackageJSONDir,
 } from "./utils";
 
 let hasExplicitDependencyOnPostCSS = false;
-let packageJsonDir;
 
 /**
  * **PostCSS Loader**
@@ -101,36 +99,58 @@ export default async function loader(content, sourceMap, meta) {
   }
 
   let result;
+  let processor;
 
   try {
-    result = await postcssFactory(plugins).process(
-      root || content,
-      processOptions
-    );
+    processor = postcssFactory(plugins);
+    result = await processor.process(root || content, processOptions);
   } catch (error) {
-    // The `findPackageJsonDir` function returns `string` or `null`.
-    // This is used to do for caching, that is, an explicit comparison with `undefined`
-    // is used to make the condition body run once.
-    if (packageJsonDir === undefined) {
-      packageJsonDir = findPackageJsonDir(process.cwd(), this.fs.statSync);
-    }
     // Check postcss versions to avoid using PostCSS 7.
     // For caching reasons, we use the readFileSync and existsSync functions from the context,
     // not the functions from the `fs` module.
-    if (
-      !hasExplicitDependencyOnPostCSS &&
-      postcssFactory().version.startsWith("7.") &&
-      packageJsonDir
-    ) {
-      const filePath = path.resolve(packageJsonDir, "package.json");
-      const pkg = parsePackageJson(filePath, this.fs.readFileSync);
-      if (!pkg.dependencies.postcss && !pkg.devDependencies.postcss) {
-        this.emitWarning(
-          "Add postcss as project dependency. postcss is not a peer dependency for postcss-loader. " +
-            "Use `npm install postcss` or `yarn add postcss`"
-        );
-      } else {
-        hasExplicitDependencyOnPostCSS = true;
+    if (!hasExplicitDependencyOnPostCSS && processor.version.startsWith("7.")) {
+      // The `findPackageJsonDir` function returns `string` or `null`.
+      // This is used to do for caching, that is, an explicit comparison with `undefined`
+      // is used to make the condition body run once.
+      const packageJSONDir = findPackageJSONDir(
+        process.cwd(),
+        this.fs.statSync
+      );
+
+      if (packageJSONDir) {
+        let bufferOfPackageJSON;
+
+        try {
+          bufferOfPackageJSON = this.fs.readFileSync(
+            path.resolve(packageJSONDir, "package.json"),
+            "utf8"
+          );
+        } catch (_error) {
+          // Nothing
+        }
+
+        if (bufferOfPackageJSON) {
+          let pkg;
+
+          try {
+            pkg = JSON.parse(bufferOfPackageJSON);
+          } catch (_error) {
+            // Nothing
+          }
+
+          if (pkg) {
+            if (!pkg.dependencies.postcss && !pkg.devDependencies.postcss) {
+              this.emitWarning(
+                new Error(
+                  "Add postcss as project dependency. postcss is not a peer dependency for postcss-loader. " +
+                    "Use `npm install postcss` or `yarn add postcss`"
+                )
+              );
+            } else {
+              hasExplicitDependencyOnPostCSS = true;
+            }
+          }
+        }
       }
     }
 

src/utils.js

@@ -408,24 +408,28 @@ function normalizeSourceMapAfterPostcss(map, resourceContext) {
   return newMap;
 }
 
-function parsePackageJson(filePath, readFileSync) {
-  return JSON.parse(readFileSync(filePath, "utf8"));
-}
-
-function findPackageJsonDir(cwd, statSync) {
+function findPackageJSONDir(cwd, statSync) {
   let dir = cwd;
+
   for (;;) {
     try {
-      if (statSync(path.join(dir, "package.json")).isFile()) break;
-      // eslint-disable-next-line no-empty
-    } catch (error) {}
+      if (statSync(path.join(dir, "package.json")).isFile()) {
+        break;
+      }
+    } catch (error) {
+      // Nothing
+    }
+
     const parent = path.dirname(dir);
+
     if (dir === parent) {
       dir = null;
       break;
     }
+
     dir = parent;
   }
+
   return dir;
 }
 
@@ -435,6 +439,5 @@ export {
   exec,
   normalizeSourceMap,
   normalizeSourceMapAfterPostcss,
-  parsePackageJson,
-  findPackageJsonDir,
+  findPackageJSONDir,
 };

test/__snapshots__/loader.test.js.snap

@@ -1,12 +1,54 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`check postcss versions to avoid using PostCSS 7 should emit a warning if postcss version is not explicitly specified when the loader is failed: errors 1`] = `
+Array [
+  "ModuleBuildError: Module build failed (from \`replaced original path\`):
+Error: Something went wrong.
+    at Processor.process (/test/loader.test.js:216:26)
+    at Object.loader (/src/index.js:106:30)",
+]
+`;
+
 exports[`check postcss versions to avoid using PostCSS 7 should emit a warning if postcss version is not explicitly specified when the loader is failed: warnings 1`] = `
 Array [
   "ModuleWarning: Module Warning (from \`replaced original path\`):
-(Emitted value instead of an instance of Error) Add postcss as project dependency. postcss is not a peer dependency for postcss-loader. Use \`npm install postcss\` or \`yarn add postcss\`",
+Add postcss as project dependency. postcss is not a peer dependency for postcss-loader. Use \`npm install postcss\` or \`yarn add postcss\`",
+]
+`;
+
+exports[`check postcss versions to avoid using PostCSS 7 should not show a warning if 'package.json' file was not found: errors 1`] = `
+Array [
+  "ModuleBuildError: Module build failed (from \`replaced original path\`):
+Error: Something went wrong.
+    at Processor.process (/test/loader.test.js:294:28)
+    at Object.loader (/src/index.js:106:30)",
 ]
 `;
 
+exports[`check postcss versions to avoid using PostCSS 7 should not show a warning if 'package.json' file was not found: warnings 1`] = `Array []`;
+
+exports[`check postcss versions to avoid using PostCSS 7 should not show a warning if 'postcss' version is explicitly defined in 'dependencies': errors 1`] = `
+Array [
+  "ModuleBuildError: Module build failed (from \`replaced original path\`):
+Error: Something went wrong.
+    at Processor.process (/test/loader.test.js:242:26)
+    at Object.loader (/src/index.js:106:30)",
+]
+`;
+
+exports[`check postcss versions to avoid using PostCSS 7 should not show a warning if 'postcss' version is explicitly defined in 'dependencies': warnings 1`] = `Array []`;
+
+exports[`check postcss versions to avoid using PostCSS 7 should not show a warning if 'postcss' version is explicitly defined in 'devDependencies': errors 1`] = `
+Array [
+  "ModuleBuildError: Module build failed (from \`replaced original path\`):
+Error: Something went wrong.
+    at Processor.process (/test/loader.test.js:268:28)
+    at Object.loader (/src/index.js:106:30)",
+]
+`;
+
+exports[`check postcss versions to avoid using PostCSS 7 should not show a warning if 'postcss' version is explicitly defined in 'devDependencies': warnings 1`] = `Array []`;
+
 exports[`loader should emit asset using the "messages" API: errors 1`] = `Array []`;
 
 exports[`loader should emit asset using the "messages" API: warnings 1`] = `Array []`;

test/fixtures/package-json-files/no-postcss/package.json

@@ -0,0 +1,4 @@
+{
+  "dependencies": {},
+  "devDependencies": {}
+}

test/fixtures/package-json-files/postcss-v8-in-dependencies/package.json

@@ -0,0 +1,6 @@
+{
+  "dependencies": {
+    "postcss": "^8.0.0"
+  },
+  "devDependencies": {}
+}

test/fixtures/package-json-files/postcss-v8-in-devDependencies/package.json

@@ -0,0 +1,6 @@
+{
+  "dependencies": {},
+  "devDependencies": {
+    "postcss": "^8.0.0"
+  }
+}

test/loader.test.js

@@ -200,50 +200,113 @@ describe("loader", () => {
 });
 
 describe("check postcss versions to avoid using PostCSS 7", () => {
-  async function getStats() {
+  it("should emit a warning if postcss version is not explicitly specified when the loader is failed", async () => {
+    const spy = jest
+      .spyOn(utils, "findPackageJSONDir")
+      .mockReturnValue(
+        path.resolve(__dirname, "./fixtures/package-json-files/no-postcss")
+      );
+
     const compiler = getCompiler("./css/index.js", {
       implementation: (...args) => {
         const result = postcss(...args);
+
         result.version = "7.0.0";
         result.process = () =>
           Promise.reject(new Error("Something went wrong."));
+
         return result;
       },
     });
+    const stats = await compile(compiler);
+
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
 
-    return compile(compiler);
-  }
+    spy.mockRestore();
+  });
 
-  it("should emit a warning if postcss version is not explicitly specified when the loader is failed", async () => {
-    jest
-      .spyOn(utils, "parsePackageJson")
-      .mockReturnValue({ dependencies: {}, devDependencies: {} });
+  it("should not show a warning if 'postcss' version is explicitly defined in 'dependencies'", async () => {
+    const spy = jest
+      .spyOn(utils, "findPackageJSONDir")
+      .mockReturnValue(
+        path.resolve(
+          __dirname,
+          "./fixtures/package-json-files/postcss-v8-in-dependencies"
+        )
+      );
+
+    const compiler = getCompiler("./css/index.js", {
+      implementation: (...args) => {
+        const result = postcss(...args);
 
-    const stats = await getStats();
+        result.version = "7.0.0";
+        result.process = () =>
+          Promise.reject(new Error("Something went wrong."));
+
+        return result;
+      },
+    });
+    const stats = await compile(compiler);
 
     expect(getWarnings(stats)).toMatchSnapshot("warnings");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
+
+    spy.mockRestore();
   });
 
-  it("should not show a warning if postcss version is explicitly defined", async () => {
-    jest.spyOn(utils, "parsePackageJson").mockReturnValue({
-      dependencies: {},
-      devDependencies: { postcss: "8.0.0" },
+  it("should not show a warning if 'postcss' version is explicitly defined in 'devDependencies'", async () => {
+    const spy = jest
+      .spyOn(utils, "findPackageJSONDir")
+      .mockReturnValue(
+        path.resolve(
+          __dirname,
+          "./fixtures/package-json-files/postcss-v8-in-devDependencies"
+        )
+      );
+
+    const compiler = getCompiler("./css/index.js", {
+      implementation: (...args) => {
+        const result = postcss(...args);
+
+        result.version = "7.0.0";
+        result.process = () =>
+          Promise.reject(new Error("Something went wrong."));
+
+        return result;
+      },
     });
+    const stats = await compile(compiler);
 
-    const stats = await getStats();
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
 
-    expect(stats.compilation.warnings.length).toBe(0);
+    spy.mockRestore();
   });
 
-  it("should not show a warning if the package.json file was not found", async () => {
-    jest.spyOn(utils, "findPackageJsonDir").mockReturnValue(null);
-    jest.spyOn(utils, "parsePackageJson").mockReturnValue({
-      dependencies: {},
-      devDependencies: { postcss: "8.0.0" },
+  it("should not show a warning if 'package.json' file was not found", async () => {
+    const spy = jest
+      .spyOn(utils, "findPackageJSONDir")
+      .mockReturnValue(
+        path.resolve(__dirname, "./fixtures/package-json-files/unknown")
+      );
+
+    const compiler = getCompiler("./css/index.js", {
+      implementation: (...args) => {
+        const result = postcss(...args);
+
+        result.version = "7.0.0";
+        result.process = () =>
+          Promise.reject(new Error("Something went wrong."));
+
+        return result;
+      },
     });
+    const stats = await compile(compiler);
 
-    const stats = await getStats();
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
 
-    expect(stats.compilation.warnings.length).toBe(0);
+    spy.mockRestore();
   });
 });