A new rule that makes sure the user have explained the reason of reverting

commitlint.config.ts

@@ -1,4 +1,4 @@
-import { Helpers } from "./commitlint/helpers";
+import { Helpers, When } from "./commitlint/helpers";
 import { Plugins } from "./commitlint/plugins";
 import { RuleConfigSeverity } from "@commitlint/types";
 
@@ -13,48 +13,55 @@ function notNullStringErrorMessage(stringType: string): string {
 module.exports = {
     parserPreset: "conventional-changelog-conventionalcommits",
     rules: {
-        "body-leading-blank": [RuleConfigSeverity.Error, "always"],
+        "body-leading-blank": [RuleConfigSeverity.Error, When.Always],
         "body-soft-max-line-length": [
             RuleConfigSeverity.Error,
-            "always",
+            When.Always,
             bodyMaxLineLength,
         ],
-        "body-paragraph-line-min-length": [RuleConfigSeverity.Error, "always"],
-        "empty-wip": [RuleConfigSeverity.Error, "always"],
-        "footer-leading-blank": [RuleConfigSeverity.Warning, "always"],
+        "body-paragraph-line-min-length": [
+            RuleConfigSeverity.Error,
+            When.Always,
+        ],
+        "empty-wip": [RuleConfigSeverity.Error, When.Always],
+        "footer-leading-blank": [RuleConfigSeverity.Warning, When.Always],
         "footer-max-line-length": [
             RuleConfigSeverity.Error,
-            "always",
+            When.Always,
             footerMaxLineLength,
         ],
-        "footer-notes-misplacement": [RuleConfigSeverity.Error, "always"],
-        "footer-refs-validity": [RuleConfigSeverity.Error, "always"],
+        "footer-notes-misplacement": [RuleConfigSeverity.Error, When.Always],
+        "footer-refs-validity": [RuleConfigSeverity.Error, When.Always],
         "header-max-length-with-suggestions": [
             RuleConfigSeverity.Error,
-            "always",
+            When.Always,
             headerMaxLineLength,
         ],
-        "subject-full-stop": [RuleConfigSeverity.Error, "never", "."],
-        "type-space-after-colon": [RuleConfigSeverity.Error, "always"],
-        "subject-lowercase": [RuleConfigSeverity.Error, "always"],
-        "body-prose": [RuleConfigSeverity.Error, "always"],
-        "type-space-after-comma": [RuleConfigSeverity.Error, "always"],
-        "trailing-whitespace": [RuleConfigSeverity.Error, "always"],
-        "prefer-slash-over-backslash": [RuleConfigSeverity.Error, "always"],
-        "type-space-before-paren": [RuleConfigSeverity.Error, "always"],
-        "type-with-square-brackets": [RuleConfigSeverity.Error, "always"],
-        "proper-issue-refs": [RuleConfigSeverity.Error, "always"],
-        "too-many-spaces": [RuleConfigSeverity.Error, "always"],
-        "commit-hash-alone": [RuleConfigSeverity.Error, "always"],
-        "title-uppercase": [RuleConfigSeverity.Error, "always"],
+        "subject-full-stop": [RuleConfigSeverity.Error, When.Never, "."],
+        "type-space-after-colon": [RuleConfigSeverity.Error, When.Always],
+        "subject-lowercase": [RuleConfigSeverity.Error, When.Always],
+        "body-prose": [RuleConfigSeverity.Error, When.Always],
+        "type-space-after-comma": [RuleConfigSeverity.Error, When.Always],
+        "trailing-whitespace": [RuleConfigSeverity.Error, When.Always],
+        "prefer-slash-over-backslash": [RuleConfigSeverity.Error, When.Always],
+        "type-space-before-paren": [RuleConfigSeverity.Error, When.Always],
+        "type-with-square-brackets": [RuleConfigSeverity.Error, When.Always],
+        "proper-issue-refs": [RuleConfigSeverity.Error, When.Always],
+        "too-many-spaces": [RuleConfigSeverity.Error, When.Always],
+        "commit-hash-alone": [RuleConfigSeverity.Error, When.Always],
+        "title-uppercase": [RuleConfigSeverity.Error, When.Always],
 
         // disabled because most of the time it doesn't work, due to https://github.com/conventional-changelog/commitlint/issues/3404
         // and anyway we were using this rule only as a warning, not an error (because a scope is not required, e.g. when too broad)
-        "type-empty": [RuleConfigSeverity.Disabled, "never"],
+        "type-empty": [RuleConfigSeverity.Disabled, When.Never],
+        "default-revert-message": [RuleConfigSeverity.Error, When.Never],
     },
+
+    // Commitlint automatically ignores some kinds of commits like Revert commit messages.
+    // We need to set this value to false to apply our rules on these messages.
+    defaultIgnores: false,
     plugins: [
         // TODO (ideas for more rules):
-        // * Detect reverts which have not been elaborated.
         // * Reject some stupid obvious words: change, update, modify (if first word after colon, error; otherwise warning).
         // * Think of how to reject this shitty commit message: https://github.com/nblockchain/NOnion/pull/34/commits/9ffcb373a1147ed1c729e8aca4ffd30467255594
         // * Workflow: detect if wip commit in a branch not named "wip/*" or whose name contains "squashed".
@@ -142,6 +149,28 @@ module.exports = {
                     return Plugins.properIssueRefs(rawStr);
                 },
 
+                "default-revert-message": (
+                    {
+                        header,
+                        body,
+                    }: {
+                        header: any;
+                        body: any;
+                    },
+                    when: string
+                ) => {
+                    let bodyStr = Helpers.convertAnyToString(body, "body");
+                    let headerStr = Helpers.assertNotNull(
+                        Helpers.convertAnyToString(header, "header"),
+                        notNullStringErrorMessage("header")
+                    );
+                    return Plugins.defaultRevertMessage(
+                        headerStr,
+                        bodyStr,
+                        Helpers.assertWhen(when)
+                    );
+                },
+
                 "title-uppercase": ({ header }: { header: any }) => {
                     let headerStr = Helpers.assertNotNull(
                         Helpers.convertAnyToString(header, "header"),

commitlint/helpers.ts

@@ -1,3 +1,8 @@
+export enum When {
+    Never = "never",
+    Always = "always",
+}
+
 export abstract class Helpers {
     public static errMessageSuffix =
         "\nFor reference, these are the guidelines that include our commit message conventions: https://github.com/nblockchain/conventions/blob/master/WorkflowGuidelines.md";
@@ -37,6 +42,15 @@ export abstract class Helpers {
         return text as string;
     }
 
+    public static assertWhen(when: string) {
+        if (when !== When.Never && when !== When.Always) {
+            throw new Error(
+                'Variable "when" should be either "never" or "always"'
+            );
+        }
+        return when as When;
+    }
+
     public static assertCharacter(letter: string) {
         if (letter.length !== 1) {
             throw Error("This function expects a character as input");

commitlint/plugins.test.ts

@@ -846,6 +846,74 @@ test("proper-issue-refs5", () => {
     expect(properIssueRefs5.status).not.toBe(0);
 });
 
+test("default-revert-message1", () => {
+    let commitMsgWithoutDefaultRevertMessage =
+        'Revert "add abbreviations.ts"\n\n' +
+        "This reverts commit 0272f587c7eece147e8d1756116b0b43e11c34ac.";
+    let defaultRevertMessage1 = runCommitLintOnMsg(
+        commitMsgWithoutDefaultRevertMessage
+    );
+    expect(defaultRevertMessage1.status).not.toBe(0);
+});
+
+test("default-revert-message2", () => {
+    let commitMsgWithDefaultRevertMessage =
+        'Revert "add abbreviations.ts"\n\n' +
+        "This reverts commit 0272f587c7eece147e8d1756116b0b43e11c34ac\n" +
+        "because/otherwise bla bla.";
+    let defaultRevertMessage2 = runCommitLintOnMsg(
+        commitMsgWithDefaultRevertMessage
+    );
+    expect(defaultRevertMessage2.status).toBe(0);
+});
+
+test("default-revert-message3", () => {
+    let commitMsgWithoutDefaultRevertMessage = 'Revert "add abbreviations.ts"';
+    let defaultRevertMessage3 = runCommitLintOnMsg(
+        commitMsgWithoutDefaultRevertMessage
+    );
+    expect(defaultRevertMessage3.status).not.toBe(0);
+});
+
+test("default-revert-message4", () => {
+    let commitMsgWithDefaultRevertMessage = "Revert .NET6 upd as it broke CI";
+    let defaultRevertMessage4 = runCommitLintOnMsg(
+        commitMsgWithDefaultRevertMessage
+    );
+    expect(defaultRevertMessage4.status).toBe(0);
+});
+
+test("default-revert-message5", () => {
+    let commitMsgWithoutDefaultRevertMessage =
+        'Revert "add abbreviations.ts"\n\n' +
+        "This reverts commit 0272f587 because bla bla.\n";
+
+    let defaultRevertMessage5 = runCommitLintOnMsg(
+        commitMsgWithoutDefaultRevertMessage
+    );
+    expect(defaultRevertMessage5.status).toBe(0);
+});
+
+test("default-revert-message6", () => {
+    let commitMsgWithDefaultRevertMessage =
+        'Revert "process overhaul" to fix CI\n\n';
+
+    let defaultRevertMessage6 = runCommitLintOnMsg(
+        commitMsgWithDefaultRevertMessage
+    );
+    expect(defaultRevertMessage6.status).toBe(0);
+});
+
+test("default-revert-message7", () => {
+    let commitMsgWithoutDefaultRevertMessage =
+        "This is a revert commit\n\nBla bla.";
+
+    let defaultRevertMessage7 = runCommitLintOnMsg(
+        commitMsgWithoutDefaultRevertMessage
+    );
+    expect(defaultRevertMessage7.status).toBe(0);
+});
+
 test("subject-lowercase1", () => {
     let commitMsgWithUppercaseAfterColon = "foo: Bar baz";
     let subjectLowerCase1 = runCommitLintOnMsg(

commitlint/plugins.ts

@@ -1,5 +1,5 @@
 import { abbr } from "./abbreviations";
-import { Helpers } from "./helpers";
+import { Helpers, When } from "./helpers";
 
 export abstract class Plugins {
     public static bodyProse(rawStr: string) {
@@ -278,6 +278,44 @@ export abstract class Plugins {
         ];
     }
 
+    public static defaultRevertMessage(
+        headerStr: string,
+        bodyStr: string | null,
+        when: When
+    ) {
+        let offence = false;
+        let isRevertCommitMessage = headerStr.toLowerCase().includes("revert");
+
+        const negated = when === "never";
+
+        if (isRevertCommitMessage) {
+            let isDefaultRevertHeader =
+                headerStr.match(/^[Rr]evert ".+"$/) !== null;
+
+            if (isDefaultRevertHeader) {
+                if (bodyStr !== null) {
+                    let lines = bodyStr.split("\n");
+                    offence =
+                        lines.length == 1 &&
+                        // 40 is the length of git commit hash.
+                        lines[0].match(/^This reverts commit [^ ]{40}\.$/) !==
+                            null;
+                } else {
+                    offence = true;
+                }
+            }
+
+            offence = negated ? offence : !offence;
+        }
+        return [
+            !offence,
+            (negated
+                ? `Please explain why you're reverting.`
+                : `Please don't change the default revert commit message.`) +
+                Helpers.errMessageSuffix,
+        ];
+    }
+
     public static titleUppercase(headerStr: string) {
         let firstWord = headerStr.split(" ")[0];
         let offence =