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fix: Emit warning when empty config file is used (#19399)
* fix: Emit warning when empty config file is used fixes #19044 * Update lib/config/config-loader.js Co-authored-by: Milos Djermanovic <[email protected]> * Update lib/config/config-loader.js Co-authored-by: Milos Djermanovic <[email protected]> * Update tests * Fix tests --------- Co-authored-by: Milos Djermanovic <[email protected]>
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-14
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‎lib/config/config-loader.js

+34-4
Original file line numberDiff line numberDiff line change
@@ -499,11 +499,41 @@ class ConfigLoader {
499499
debug(`Loading config file ${configFilePath}`);
500500
const fileConfig = await loadConfigFile(configFilePath);
501501

502-
if (Array.isArray(fileConfig)) {
503-
configs.push(...fileConfig);
504-
} else {
505-
configs.push(fileConfig);
502+
/*
503+
* It's possible that a config file could be empty or else
504+
* have an empty object or array. In this case, we want to
505+
* warn the user that they have an empty config.
506+
*
507+
* An empty CommonJS file exports an empty object while
508+
* an empty ESM file exports undefined.
509+
*/
510+
511+
let emptyConfig = typeof fileConfig === "undefined";
512+
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debug(`Config file ${configFilePath} is ${emptyConfig ? "empty" : "not empty"}`);
514+
515+
if (!emptyConfig) {
516+
if (Array.isArray(fileConfig)) {
517+
if (fileConfig.length === 0) {
518+
debug(`Config file ${configFilePath} is an empty array`);
519+
emptyConfig = true;
520+
} else {
521+
configs.push(...fileConfig);
522+
}
523+
} else {
524+
if (typeof fileConfig === "object" && fileConfig !== null && Object.keys(fileConfig).length === 0) {
525+
debug(`Config file ${configFilePath} is an empty object`);
526+
emptyConfig = true;
527+
} else {
528+
configs.push(fileConfig);
529+
}
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}
506531
}
532+
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if (emptyConfig) {
534+
globalThis.process?.emitWarning?.(`Running ESLint with an empty config (from ${configFilePath}). Please double-check that this is what you want. If you want to run ESLint with an empty config, export [{}] to remove this warning.`, "ESLintEmptyConfigWarning");
535+
}
536+
507537
}
508538

509539
// add in any configured defaults

‎tests/fixtures/empty-config-file/cjs/eslint.config.cjs

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
// intentionally empty

‎tests/fixtures/empty-config-file/cjs/foo.js

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
let foo = "bar";

‎tests/fixtures/empty-config-file/esm/eslint.config.empty-array.mjs

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
export default [];

‎tests/fixtures/empty-config-file/esm/eslint.config.mjs

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
// intentionally empty

‎tests/fixtures/empty-config-file/esm/eslint.config.null.mjs

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
export default null;

‎tests/fixtures/empty-config-file/esm/eslint.config.zero.mjs

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
export default 0;

‎tests/fixtures/empty-config-file/esm/foo.js

+1
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
let foo = "bar";

‎tests/lib/config/config-loader.js

+93
Original file line numberDiff line numberDiff line change
@@ -83,6 +83,99 @@ describe("Config loaders", () => {
8383
assert.strictEqual(locateConfigFileToUse.callCount, 1, "Expected `ConfigLoader.locateConfigFileToUse` to be called exactly once");
8484
assert.strictEqual(calculateConfigArray.callCount, 1, "Expected `ConfigLoader.calculateConfigArray` to be called exactly once");
8585
});
86+
87+
it("should not error when loading an empty CommonJS config file", async () => {
88+
const cwd = path.resolve(fixtureDir, "empty-config-file");
89+
90+
const configLoader = new ConfigLoaderClass({
91+
cwd,
92+
ignoreEnabled: true,
93+
configFile: "cjs/eslint.config.cjs"
94+
});
95+
96+
const emitWarning = sinon.stub(process, "emitWarning");
97+
const configArray = await configLoader.loadConfigArrayForFile(path.resolve(cwd, "cjs/foo.js"));
98+
99+
assert(Array.isArray(configArray), "Expected `loadConfigArrayForFile()` to return a config array");
100+
assert(emitWarning.called, "Expected `process.emitWarning` to be called");
101+
assert.strictEqual(emitWarning.args[0][1], "ESLintEmptyConfigWarning", "Expected `process.emitWarning` to be called with 'ESLintEmptyConfigWarning' as the second argument");
102+
});
103+
104+
it("should not error when loading an empty ESM config file", async () => {
105+
const cwd = path.resolve(fixtureDir, "empty-config-file");
106+
107+
const configLoader = new ConfigLoaderClass({
108+
cwd,
109+
ignoreEnabled: true,
110+
configFile: "esm/eslint.config.mjs"
111+
});
112+
113+
const emitWarning = sinon.stub(process, "emitWarning");
114+
const configArray = await configLoader.loadConfigArrayForFile(path.resolve(cwd, "esm/foo.js"));
115+
116+
assert(Array.isArray(configArray), "Expected `loadConfigArrayForFile()` to return a config array");
117+
assert(emitWarning.called, "Expected `process.emitWarning` to be called");
118+
assert.strictEqual(emitWarning.args[0][1], "ESLintEmptyConfigWarning", "Expected `process.emitWarning` to be called with 'ESLintEmptyConfigWarning' as the second argument");
119+
});
120+
121+
it("should not error when loading an ESM config file with an empty array", async () => {
122+
const cwd = path.resolve(fixtureDir, "empty-config-file");
123+
124+
const configLoader = new ConfigLoaderClass({
125+
cwd,
126+
ignoreEnabled: true,
127+
configFile: "esm/eslint.config.empty-array.mjs"
128+
});
129+
130+
const emitWarning = sinon.stub(process, "emitWarning");
131+
const configArray = await configLoader.loadConfigArrayForFile(path.resolve(cwd, "mjs/foo.js"));
132+
133+
assert(Array.isArray(configArray), "Expected `loadConfigArrayForFile()` to return a config array");
134+
assert(emitWarning.called, "Expected `process.emitWarning` to be called");
135+
assert.strictEqual(emitWarning.args[0][1], "ESLintEmptyConfigWarning", "Expected `process.emitWarning` to be called with 'ESLintEmptyConfigWarning' as the second argument");
136+
});
137+
138+
it("should throw an error when loading an ESM config file with null", async () => {
139+
const cwd = path.resolve(fixtureDir, "empty-config-file");
140+
141+
const configLoader = new ConfigLoaderClass({
142+
cwd,
143+
ignoreEnabled: true,
144+
configFile: "esm/eslint.config.null.mjs"
145+
});
146+
147+
let error;
148+
149+
try {
150+
await configLoader.loadConfigArrayForFile(path.resolve(cwd, "mjs/foo.js"));
151+
} catch (err) {
152+
error = err;
153+
}
154+
155+
assert(error);
156+
assert.strictEqual(error.message, "Config (unnamed): Unexpected null config at user-defined index 0.");
157+
});
158+
159+
it("should throw an error when loading an ESM config with 0", async () => {
160+
const cwd = path.resolve(fixtureDir, "empty-config-file");
161+
162+
const configLoader = new ConfigLoaderClass({
163+
cwd,
164+
ignoreEnabled: true,
165+
configFile: "esm/eslint.config.zero.mjs"
166+
});
167+
168+
let error;
169+
170+
try {
171+
await configLoader.loadConfigArrayForFile(path.resolve(cwd, "mjs/foo.js"));
172+
} catch (err) {
173+
error = err;
174+
}
175+
176+
assert(error);
177+
assert.strictEqual(error.message, "Config (unnamed): Unexpected non-object config at user-defined index 0.");
178+
});
86179
});
87180

88181
describe("getCachedConfigArrayForFile()", () => {

‎tests/lib/eslint/eslint.js

+17-10
Original file line numberDiff line numberDiff line change
@@ -1389,20 +1389,23 @@ describe("ESLint", () => {
13891389
);
13901390
});
13911391

1392-
it("should fail to load a CommonJS TS config file that exports undefined with a helpful error message", async () => {
1392+
it("should fail to load a CommonJS TS config file that exports undefined with a helpful warning message", async () => {
1393+
1394+
sinon.restore();
13931395

13941396
const cwd = getFixturePath("ts-config-files", "ts");
1397+
const processStub = sinon.stub(process, "emitWarning");
13951398

13961399
eslint = new ESLint({
13971400
cwd,
13981401
flags,
13991402
overrideConfigFile: "eslint.undefined.config.ts"
14001403
});
14011404

1402-
await assert.rejects(
1403-
eslint.lintText("foo"),
1404-
{ message: "Config (unnamed): Unexpected undefined config at user-defined index 0." }
1405-
);
1405+
await eslint.lintText("foo");
1406+
1407+
assert.strictEqual(processStub.callCount, 1, "calls `process.emitWarning()` once");
1408+
assert.strictEqual(processStub.getCall(0).args[1], "ESLintEmptyConfigWarning");
14061409

14071410
});
14081411

@@ -5975,20 +5978,24 @@ describe("ESLint", () => {
59755978
);
59765979
});
59775980

5978-
it("should fail to load a CommonJS TS config file that exports undefined with a helpful error message", async () => {
5981+
it("should fail to load a CommonJS TS config file that exports undefined with a helpful warning message", async () => {
5982+
5983+
sinon.restore();
59795984

59805985
const cwd = getFixturePath("ts-config-files", "ts");
5986+
const processStub = sinon.stub(process, "emitWarning");
59815987

59825988
eslint = new ESLint({
59835989
cwd,
59845990
flags,
59855991
overrideConfigFile: "eslint.undefined.config.ts"
59865992
});
59875993

5988-
await assert.rejects(
5989-
eslint.lintFiles("foo.js"),
5990-
{ message: "Config (unnamed): Unexpected undefined config at user-defined index 0." }
5991-
);
5994+
await eslint.lintFiles("foo.js");
5995+
5996+
assert.strictEqual(processStub.callCount, 1, "calls `process.emitWarning()` once");
5997+
assert.strictEqual(processStub.getCall(0).args[1], "ESLintEmptyConfigWarning");
5998+
59925999

59936000
});
59946001

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