[postcss-less] add definitions (#46235)

* [postcss-less] add definitions

https://github.com/shellscape/postcss-less

* Remove needless `FunctionAtRule.params`

* Bump postcss to the latest

* Add `nodeToString()` type and more test cases

types/postcss-less/index.d.ts

@@ -0,0 +1,55 @@
+// Type definitions for postcss-less 3.1
+// Project: https://github.com/shellscape/postcss-less
+// Definitions by: Masafumi Koba <https://github.com/ybiquitous>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+import * as postcss from 'postcss';
+
+export = postcssLess;
+
+declare const postcssLess: postcss.Syntax & {
+    parse: postcss.Parser;
+    stringify: postcss.Stringifier;
+    nodeToString: (node: postcss.Node) => string;
+};
+
+declare namespace postcssLess {
+    // @see https://github.com/shellscape/postcss-less/blob/v3.1.4/lib/nodes/import.js
+    interface ImportAtRule extends postcss.AtRule {
+        import: true;
+        filename: string;
+        options?: string;
+    }
+
+    // @see https://github.com/shellscape/postcss-less/blob/v3.1.4/lib/nodes/variable.js
+    interface VariableAtRule extends postcss.AtRule {
+        variable: true;
+    }
+
+    // @see https://github.com/shellscape/postcss-less/blob/v3.1.4/lib/LessParser.js#L147-L151
+    interface MixinAtRule extends postcss.AtRule {
+        mixin: true;
+        important?: true;
+    }
+
+    // @see https://github.com/shellscape/postcss-less/blob/v3.1.4/lib/LessParser.js#L57
+    interface FunctionAtRule extends postcss.AtRule {
+        function: true;
+    }
+
+    type AtRule = ImportAtRule | VariableAtRule | MixinAtRule | FunctionAtRule;
+
+    // @see https://github.com/shellscape/postcss-less/blob/v3.1.4/lib/LessParser.js#L187
+    interface ExtendRule extends postcss.Rule {
+        extend: true;
+    }
+
+    type Rule = ExtendRule;
+
+    // @see https://github.com/shellscape/postcss-less/blob/v3.1.4/lib/LessParser.js#L73
+    interface InlineComment extends postcss.Comment {
+        inline: true;
+    }
+
+    type Comment = InlineComment;
+}

types/postcss-less/package.json

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+{
+  "private": true,
+  "dependencies": {
+    "postcss": "^7.0.32"
+  }
+}

types/postcss-less/postcss-less-tests.ts

@@ -0,0 +1,71 @@
+import postcss = require('postcss');
+import less = require('postcss-less');
+
+const lessCode = 'a { @link-color: blue; }';
+
+postcss().process(lessCode, { syntax: less });
+
+less.parse(lessCode).walkAtRules(atRule => {
+    const lessAtRule = atRule as less.AtRule;
+
+    if ('import' in lessAtRule) {
+        assert(lessAtRule.import === true);
+        assert(typeof lessAtRule.filename === 'string');
+
+        const { options } = lessAtRule;
+        if (options) {
+            assert(typeof options === 'string');
+        } else {
+            assert(options === undefined);
+        }
+    }
+
+    if ('variable' in lessAtRule) {
+        assert(lessAtRule.variable === true);
+    }
+
+    if ('mixin' in lessAtRule) {
+        assert(lessAtRule.mixin === true);
+
+        const { important } = lessAtRule;
+        if (important) {
+            assert(important === true);
+        } else {
+            assert(important === undefined);
+        }
+    }
+
+    if ('function' in lessAtRule) {
+        assert(lessAtRule.function === true);
+    }
+});
+
+less.parse(lessCode).walkRules(rule => {
+    const lessRule = rule as less.Rule;
+    assert(lessRule.extend === true);
+});
+
+less.parse(lessCode).walkComments(comment => {
+    const lessComment = comment as less.Comment;
+    assert(lessComment.inline === true);
+});
+
+less.stringify(less.parse(lessCode), (part, node, type) => {
+    assert(typeof part === 'string');
+    assert(type === 'start');
+    assert(type === 'end');
+
+    if (node) {
+        assert(typeof node.root === 'function');
+    } else {
+        assert(node === undefined);
+    }
+});
+
+assert(typeof less.nodeToString(less.parse(lessCode)) === 'string');
+
+function assert(condition: any) /* : asserts condition */ {
+    if (!condition) {
+        throw new Error('Assertion failed');
+    }
+}

types/postcss-less/tsconfig.json

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+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictFunctionTypes": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "postcss-less-tests.ts"
+    ]
+}

types/postcss-less/tslint.json

@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }