New Rule one contract per file

conf/rulesets/solhint-all.js

@@ -16,6 +16,7 @@ module.exports = Object.freeze({
     'no-global-import': 'warn',
     'no-unused-import': 'warn',
     'no-unused-vars': 'warn',
+    'one-contract-per-file': 'warn',
     'payable-fallback': 'warn',
     'reason-string': [
       'warn',

conf/rulesets/solhint-recommended.js

@@ -13,6 +13,7 @@ module.exports = Object.freeze({
     'no-global-import': 'warn',
     'no-unused-import': 'warn',
     'no-unused-vars': 'warn',
+    'one-contract-per-file': 'warn',
     'payable-fallback': 'warn',
     'reason-string': [
       'warn',

docs/rules.md

@@ -6,22 +6,23 @@ title:       "Rule Index of Solhint"
 
 ## Best Practise Rules
 
-| Rule Id                                                            | Error                                                                                                                 | Recommended  | Deprecated |
-| ------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------- | ------------ | ---------- |
-| [code-complexity](./rules/best-practises/code-complexity.md)       | Function has cyclomatic complexity "current" but allowed no more than maxcompl.                                       |              |            |
-| [custom-errors](./rules/best-practises/custom-errors.md)           | Enforces the use of Custom Errors over Require and Revert statements                                                  | $~~~~~~~~$✔️ |            |
-| [explicit-types](./rules/best-practises/explicit-types.md)         | Forbid or enforce explicit types (like uint256) that have an alias (like uint).                                       | $~~~~~~~~$✔️ |            |
-| [function-max-lines](./rules/best-practises/function-max-lines.md) | Function body contains "count" lines but allowed no more than maxlines.                                               |              |            |
-| [max-line-length](./rules/best-practises/max-line-length.md)       | Line length must be no more than maxlen.                                                                              |              |            |
-| [max-states-count](./rules/best-practises/max-states-count.md)     | Contract has "some count" states declarations but allowed no more than maxstates.                                     | $~~~~~~~~$✔️ |            |
-| [no-console](./rules/best-practises/no-console.md)                 | No console.log/logInt/logBytesX/logString/etc & No hardhat and forge-std console.sol import statements.               | $~~~~~~~~$✔️ |            |
-| [no-empty-blocks](./rules/best-practises/no-empty-blocks.md)       | Code block has zero statements inside. Exceptions apply.                                                              | $~~~~~~~~$✔️ |            |
-| [no-global-import](./rules/best-practises/no-global-import.md)     | Import statement includes an entire file instead of selected symbols.                                                 | $~~~~~~~~$✔️ |            |
-| [no-unused-import](./rules/best-practises/no-unused-import.md)     | Imported object name is not being used by the contract.                                                               | $~~~~~~~~$✔️ |            |
-| [no-unused-vars](./rules/best-practises/no-unused-vars.md)         | Variable "name" is unused.                                                                                            | $~~~~~~~~$✔️ |            |
-| [payable-fallback](./rules/best-practises/payable-fallback.md)     | When fallback is not payable you will not be able to receive ethers.                                                  | $~~~~~~~~$✔️ |            |
-| [reason-string](./rules/best-practises/reason-string.md)           | Require or revert statement must have a reason string and check that each reason string is at most N characters long. | $~~~~~~~~$✔️ |            |
-| [constructor-syntax](./rules/best-practises/constructor-syntax.md) | Constructors should use the new constructor keyword.                                                                  |              |            |
+| Rule Id                                                                  | Error                                                                                                                                      | Recommended  | Deprecated |
+| ------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------ | ------------ | ---------- |
+| [code-complexity](./rules/best-practises/code-complexity.md)             | Function has cyclomatic complexity "current" but allowed no more than maxcompl.                                                            |              |            |
+| [custom-errors](./rules/best-practises/custom-errors.md)                 | Enforces the use of Custom Errors over Require and Revert statements                                                                       | $~~~~~~~~$✔️ |            |
+| [explicit-types](./rules/best-practises/explicit-types.md)               | Forbid or enforce explicit types (like uint256) that have an alias (like uint).                                                            | $~~~~~~~~$✔️ |            |
+| [function-max-lines](./rules/best-practises/function-max-lines.md)       | Function body contains "count" lines but allowed no more than maxlines.                                                                    |              |            |
+| [max-line-length](./rules/best-practises/max-line-length.md)             | Line length must be no more than maxlen.                                                                                                   |              |            |
+| [max-states-count](./rules/best-practises/max-states-count.md)           | Contract has "some count" states declarations but allowed no more than maxstates.                                                          | $~~~~~~~~$✔️ |            |
+| [no-console](./rules/best-practises/no-console.md)                       | No console.log/logInt/logBytesX/logString/etc & No hardhat and forge-std console.sol import statements.                                    | $~~~~~~~~$✔️ |            |
+| [no-empty-blocks](./rules/best-practises/no-empty-blocks.md)             | Code block has zero statements inside. Exceptions apply.                                                                                   | $~~~~~~~~$✔️ |            |
+| [no-global-import](./rules/best-practises/no-global-import.md)           | Import statement includes an entire file instead of selected symbols.                                                                      | $~~~~~~~~$✔️ |            |
+| [no-unused-import](./rules/best-practises/no-unused-import.md)           | Imported object name is not being used by the contract.                                                                                    | $~~~~~~~~$✔️ |            |
+| [no-unused-vars](./rules/best-practises/no-unused-vars.md)               | Variable "name" is unused.                                                                                                                 | $~~~~~~~~$✔️ |            |
+| [one-contract-per-file](./rules/best-practises/one-contract-per-file.md) | Enforces the use of ONE Contract per file see [here](https://docs.soliditylang.org/en/v0.8.21/style-guide.html#contract-and-library-names) | $~~~~~~~~$✔️ |            |
+| [payable-fallback](./rules/best-practises/payable-fallback.md)           | When fallback is not payable you will not be able to receive ethers.                                                                       | $~~~~~~~~$✔️ |            |
+| [reason-string](./rules/best-practises/reason-string.md)                 | Require or revert statement must have a reason string and check that each reason string is at most N characters long.                      | $~~~~~~~~$✔️ |            |
+| [constructor-syntax](./rules/best-practises/constructor-syntax.md)       | Constructors should use the new constructor keyword.                                                                                       |              |            |
 
 
 ## Miscellaneous

docs/rules/best-practises/one-contract-per-file.md

@@ -0,0 +1,39 @@
+---
+warning:     "This is a dynamically generated file. Do not edit manually."
+layout:      "default"
+title:       "one-contract-per-file | Solhint"
+---
+
+# one-contract-per-file
+![Recommended Badge](https://img.shields.io/badge/-Recommended-brightgreen)
+![Category Badge](https://img.shields.io/badge/-Best%20Practise%20Rules-informational)
+![Default Severity Badge warn](https://img.shields.io/badge/Default%20Severity-warn-yellow)
+> The {"extends": "solhint:recommended"} property in a configuration file enables this rule.
+
+
+## Description
+Enforces the use of ONE Contract per file see [here](https://docs.soliditylang.org/en/v0.8.21/style-guide.html#contract-and-library-names)
+
+## Options
+This rule accepts a string option of rule severity. Must be one of "error", "warn", "off". Default to warn.
+
+### Example Config
+```json
+{
+  "rules": {
+    "one-contract-per-file": "warn"
+  }
+}
+```
+
+
+## Examples
+This rule does not have examples.
+
+## Version
+This rule is introduced in the latest version.
+
+## Resources
+- [Rule source](https://github.com/protofire/solhint/tree/master/lib/rules/best-practises/one-contract-per-file.js)
+- [Document source](https://github.com/protofire/solhint/tree/master/docs/rules/best-practises/one-contract-per-file.md)
+- [Test cases](https://github.com/protofire/solhint/tree/master/test/rules/best-practises/one-contract-per-file.js)

lib/rules/best-practises/index.js

@@ -11,6 +11,7 @@ const NoGlobalImportsChecker = require('./no-global-import')
 const NoUnusedImportsChecker = require('./no-unused-import')
 const ExplicitTypesChecker = require('./explicit-types')
 const CustomErrorsChecker = require('./custom-errors')
+const OneContractPerFileChecker = require('./one-contract-per-file')
 
 module.exports = function checkers(reporter, config, inputSrc, tokens) {
   return [
@@ -27,5 +28,6 @@ module.exports = function checkers(reporter, config, inputSrc, tokens) {
     new NoUnusedImportsChecker(reporter, tokens),
     new ExplicitTypesChecker(reporter, config),
     new CustomErrorsChecker(reporter),
+    new OneContractPerFileChecker(reporter),
   ]
 }

lib/rules/best-practises/one-contract-per-file.js

@@ -0,0 +1,51 @@
+const BaseChecker = require('../base-checker')
+const { severityDescription } = require('../../doc/utils')
+
+const DEFAULT_SEVERITY = 'warn'
+
+const ruleId = 'one-contract-per-file'
+const meta = {
+  type: 'best-practises',
+
+  docs: {
+    description:
+      'Enforces the use of ONE Contract per file see [here](https://docs.soliditylang.org/en/v0.8.21/style-guide.html#contract-and-library-names)',
+    category: 'Best Practise Rules',
+    options: [
+      {
+        description: severityDescription,
+        default: DEFAULT_SEVERITY,
+      },
+    ],
+  },
+
+  isDefault: false,
+  recommended: true,
+  defaultSetup: DEFAULT_SEVERITY,
+
+  schema: null,
+}
+
+class OneContractPerFileChecker extends BaseChecker {
+  constructor(reporter) {
+    super(reporter, ruleId, meta)
+  }
+
+  SourceUnit(node) {
+    const contractDefinitionCount = node.children.reduce((count, child) => {
+      if (child.type === 'ContractDefinition') {
+        return count + 1
+      }
+      return count
+    }, 0)
+
+    if (contractDefinitionCount > 1) {
+      this.error(
+        node,
+        `Found more than One contract per file. ${contractDefinitionCount} contracts found!`
+      )
+    }
+  }
+}
+
+module.exports = OneContractPerFileChecker

test/fixtures/best-practises/one-contract-per-file.js

@@ -0,0 +1,36 @@
+const ONE_CONTRACT = `
+    pragma solidity 0.8.0;
+
+    contract A {
+        uint256 public constant TESTA = "testA";
+    }
+    `
+
+const TWO_CONTRACTS = `
+    pragma solidity 0.8.0;
+
+    contract A {
+        uint256 public constant TESTA = "testA";
+    }
+
+    contract B {
+        uint256 public constant TESTB = "testB";
+    }
+    `
+
+const THREE_CONTRACTS = `
+    pragma solidity 0.8.0;
+
+    contract A {
+        uint256 public constant TESTA = "testA";
+    }
+
+    contract B {
+        uint256 public constant TESTB = "testB";
+    }
+
+    contract C {
+        uint256 public constant TESTC = "testC";
+    }
+    `
+module.exports = { ONE_CONTRACT, TWO_CONTRACTS, THREE_CONTRACTS }

test/rules/best-practises/one-contract-per-file.js

@@ -0,0 +1,37 @@
+const { assertNoWarnings, assertErrorMessage, assertErrorCount } = require('../../common/asserts')
+const linter = require('../../../lib/index')
+const contracts = require('../../fixtures/best-practises/one-contract-per-file')
+
+describe('Linter - one-contract-per-file', () => {
+  it('should not raise error for ONE contract only', () => {
+    const code = contracts.ONE_CONTRACT
+
+    const report = linter.processStr(code, {
+      rules: { 'one-contract-per-file': 'error' },
+    })
+
+    assertNoWarnings(report)
+  })
+
+  it('should raise error for TWO contracts in same file', () => {
+    const code = contracts.TWO_CONTRACTS
+
+    const report = linter.processStr(code, {
+      rules: { 'one-contract-per-file': 'error' },
+    })
+
+    assertErrorCount(report, 1)
+    assertErrorMessage(report, 'Found more than One contract per file. 2 contracts found!')
+  })
+
+  it('should raise error for THREE contracts in same file', () => {
+    const code = contracts.THREE_CONTRACTS
+
+    const report = linter.processStr(code, {
+      rules: { 'one-contract-per-file': 'error' },
+    })
+
+    assertErrorCount(report, 1)
+    assertErrorMessage(report, 'Found more than One contract per file. 3 contracts found!')
+  })
+})