feat: add support for pattern matching

https://www.python.org/dev/peps/pep-0636/ Fixes #116
tree-sitter · Dec 5, 2021 · b6e4254 · b6e4254
1 parent 24b530c
commit b6e4254
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Showing 9 changed files with 33,212 additions and 29,557 deletions.
diff --git a/grammar.js b/grammar.js
@@ -38,6 +38,8 @@ module.exports = grammar({
     [$.tuple, $.tuple_pattern],
     [$.list, $.list_pattern],
     [$.with_item, $._collection_elements],
+    [$.named_expression, $.as_pattern],
+    [$.match_statement, $.primary_expression],
   ],
 
   supertypes: $ => [
@@ -228,7 +230,8 @@ module.exports = grammar({
       $.with_statement,
       $.function_definition,
       $.class_definition,
-      $.decorated_definition
+      $.decorated_definition,
+      $.match_statement,
     ),
 
     if_statement: $ => seq(
@@ -253,6 +256,15 @@ module.exports = grammar({
       field('body', $._suite)
     ),
 
+    match_statement: $ => seq('match', field('subject', $.expression), ':', repeat(field('alternative', $.case_clause))),
+
+    case_clause: $ => seq(
+      'case',
+      field('pattern', $.expression),
+      ':',
+      field('consequence', $._suite)
+    ),
+
     for_statement: $ => seq(
       optional('async'),
       'for',
@@ -320,10 +332,6 @@ module.exports = grammar({
 
     with_item: $ => prec.dynamic(-1, seq(
       field('value', $.expression),
-      optional(seq(
-        'as',
-        field('alias', $.pattern)
-      ))
     )),
 
     function_definition: $ => seq(
@@ -478,6 +486,7 @@ module.exports = grammar({
 
     pattern: $ => choice(
       $.identifier,
+      alias("match", $.identifier), // ambiguity with match statement: only ":" at end of line decides if "match" keyword
       $.keyword_identifier,
       $.subscript,
       $.attribute,
@@ -522,6 +531,14 @@ module.exports = grammar({
       choice($.identifier, $.keyword_identifier, $.subscript, $.attribute)
     ),
 
+    // Extended patterns (patterns allowed in match statement are far more flexible than simple patterns
+
+    as_pattern: $ => prec.left(seq(
+      $.expression,
+      'as',
+      $.expression
+    )),
+
     // Expressions
 
     _expression_within_for_in_clause: $ => choice(
@@ -537,12 +554,14 @@ module.exports = grammar({
       $.lambda,
       $.primary_expression,
       $.conditional_expression,
-      $.named_expression
+      $.named_expression,
+      $.as_pattern
     ),
 
     primary_expression: $ => choice(
       $.binary_operator,
       $.identifier,
+      alias("match", $.identifier),
       $.keyword_identifier,
       $.string,
       $.concatenated_string,
@@ -631,8 +650,8 @@ module.exports = grammar({
             'is',
             seq('is', 'not')
           )),
-          $.primary_expression
-        ))
+        $.primary_expression
+      ))
     )),
 
     lambda: $ => prec(PREC.lambda, seq(
@@ -669,7 +688,7 @@ module.exports = grammar({
 
     _left_hand_side: $ => choice(
       $.pattern,
-      $.pattern_list
+      $.pattern_list,
     ),
 
     pattern_list: $ => seq(
@@ -952,6 +971,7 @@ module.exports = grammar({
         'exec',
         'async',
         'await',
+        'match',
       ),
       $.identifier
     )),
@@ -969,10 +989,10 @@ module.exports = grammar({
   }
 })
 
-function commaSep1 (rule) {
+function commaSep1(rule) {
   return sep1(rule, ',')
 }
 
-function sep1 (rule, separator) {
+function sep1(rule, separator) {
   return seq(rule, repeat(seq(separator, rule)))
 }
diff --git a/package.json b/package.json
@@ -10,10 +10,10 @@
   "author": "Max Brunsfeld",
   "license": "MIT",
   "dependencies": {
-    "nan": "^2.14.0"
+    "nan": "^2.15.0"
   },
   "devDependencies": {
-    "tree-sitter-cli": "^0.19.3"
+    "tree-sitter-cli": "^0.20.1"
   },
   "scripts": {
     "build": "tree-sitter generate && node-gyp build",

diff --git a/src/grammar.json b/src/grammar.json
@@ -772,6 +772,10 @@
         {
           "type": "SYMBOL",
           "name": "decorated_definition"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "match_statement"
         }
       ]
     },
@@ -881,6 +885,67 @@
         }
       ]
     },
+    "match_statement": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "match"
+        },
+        {
+          "type": "FIELD",
+          "name": "subject",
+          "content": {
+            "type": "SYMBOL",
+            "name": "expression"
+          }
+        },
+        {
+          "type": "STRING",
+          "value": ":"
+        },
+        {
+          "type": "REPEAT",
+          "content": {
+            "type": "FIELD",
+            "name": "alternative",
+            "content": {
+              "type": "SYMBOL",
+              "name": "case_clause"
+            }
+          }
+        }
+      ]
+    },
+    "case_clause": {
+      "type": "SEQ",
+      "members": [
+        {
+          "type": "STRING",
+          "value": "case"
+        },
+        {
+          "type": "FIELD",
+          "name": "pattern",
+          "content": {
+            "type": "SYMBOL",
+            "name": "expression"
+          }
+        },
+        {
+          "type": "STRING",
+          "value": ":"
+        },
+        {
+          "type": "FIELD",
+          "name": "consequence",
+          "content": {
+            "type": "SYMBOL",
+            "name": "_suite"
+          }
+        }
+      ]
+    },
     "for_statement": {
       "type": "SEQ",
       "members": [
@@ -1260,31 +1325,6 @@
               "type": "SYMBOL",
               "name": "expression"
             }
-          },
-          {
-            "type": "CHOICE",
-            "members": [
-              {
-                "type": "SEQ",
-                "members": [
-                  {
-                    "type": "STRING",
-                    "value": "as"
-                  },
-                  {
-                    "type": "FIELD",
-                    "name": "alias",
-                    "content": {
-                      "type": "SYMBOL",
-                      "name": "pattern"
-                    }
-                  }
-                ]
-              },
-              {
-                "type": "BLANK"
-              }
-            ]
           }
         ]
       }
@@ -2046,6 +2086,15 @@
           "type": "SYMBOL",
           "name": "identifier"
         },
+        {
+          "type": "ALIAS",
+          "content": {
+            "type": "STRING",
+            "value": "match"
+          },
+          "named": true,
+          "value": "identifier"
+        },
         {
           "type": "SYMBOL",
           "name": "keyword_identifier"
@@ -2248,6 +2297,27 @@
         }
       ]
     },
+    "as_pattern": {
+      "type": "PREC_LEFT",
+      "value": 0,
+      "content": {
+        "type": "SEQ",
+        "members": [
+          {
+            "type": "SYMBOL",
+            "name": "expression"
+          },
+          {
+            "type": "STRING",
+            "value": "as"
+          },
+          {
+            "type": "SYMBOL",
+            "name": "expression"
+          }
+        ]
+      }
+    },
     "_expression_within_for_in_clause": {
       "type": "CHOICE",
       "members": [
@@ -2300,6 +2370,10 @@
         {
           "type": "SYMBOL",
           "name": "named_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "as_pattern"
         }
       ]
     },
@@ -2314,6 +2388,15 @@
           "type": "SYMBOL",
           "name": "identifier"
         },
+        {
+          "type": "ALIAS",
+          "content": {
+            "type": "STRING",
+            "value": "match"
+          },
+          "named": true,
+          "value": "identifier"
+        },
         {
           "type": "SYMBOL",
           "name": "keyword_identifier"
@@ -4831,6 +4914,10 @@
             {
               "type": "STRING",
               "value": "await"
+            },
+            {
+              "type": "STRING",
+              "value": "match"
             }
           ]
         },
@@ -4914,6 +5001,14 @@
     [
       "with_item",
       "_collection_elements"
+    ],
+    [
+      "named_expression",
+      "as_pattern"
+    ],
+    [
+      "match_statement",
+      "primary_expression"
     ]
   ],
   "precedences": [],