JavaScript: extract variables and constants in destructuring assignment

Close #1112.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>

Units/parser-javascript.r/js-destructural-binding.d/args.ctags

@@ -0,0 +1 @@
+--sort=no

Units/parser-javascript.r/js-destructural-binding.d/input.js

@@ -0,0 +1,56 @@
+// Derrived from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment
+const [x] = [1];
+const [y, z] = [1, 2, 3, 4, 5];
+let [a=5, b=7] = [1];
+
+let [c, , d] = [1, 2, 3];
+let [e, f = 0, , g] = [1, 2, 3, 4];
+
+let [,,] = [1, 2, 3];
+let [,]  = [1, 2, 3];
+let []   = [1, 2, 3];
+
+const [h, i, ...[j, k]] = [1, 2, 3, 4];
+const [l, m, ...[n, o, ...[p, q]]] = [1, 2, 3, 4, 5, 6];
+
+const [A, B, ...{ C, D }] = []
+
+const user = {
+    E: 42,
+    F: true
+};
+
+const {E, F} = user;
+
+const {E: G, F: H} = user;
+
+
+const {I = 10, J = 5} = {I: 3};
+
+let {a: K = 10, b: L = 5} = {a: 3};
+
+let {M, N, ...O} = {M: 10, N: 20, c: 30, d: 40}
+
+
+const metadata = {
+  title: 'Scratchpad',
+  translations: [
+    {
+      locale: 'de',
+      localization_tags: [],
+      last_edit: '2014-04-14T08:43:37',
+      url: '/de/docs/Tools/Scratchpad',
+      title: 'JavaScript-Umgebung'
+    }
+  ],
+  url: '/en-US/docs/Tools/Scratchpad'
+};
+
+let {
+  title: englishTitle, // rename
+  translations: [
+    {
+       title: localeTitle, // rename
+    },
+  ],
+} = metadata;

Units/parser-javascript.r/js-destructural-binding.d/validator

@@ -0,0 +1 @@
+node

parsers/jscript.c

@@ -2252,6 +2252,121 @@ static bool parseES6Class (tokenInfo *const token, const tokenInfo *targetName)
 	return true;
 }
 
+static void parseObjectDestructuring (tokenInfo *const token, bool is_const);
+static void parseArrayDestructuring (tokenInfo *const token, bool is_const)
+{
+	int nest_level = 1;
+	bool in_left_side = true;
+
+	while (nest_level > 0 && ! isType (token, TOKEN_EOF))
+	{
+		readToken (token);
+		if (isType (token, TOKEN_OPEN_SQUARE))
+		{
+			in_left_side = true;
+			nest_level++;
+		}
+		else if (isType (token, TOKEN_CLOSE_SQUARE))
+		{
+			in_left_side = false;
+			nest_level--;
+		}
+		else if (isType (token, TOKEN_OPEN_CURLY))
+		{
+			in_left_side = false;
+			parseObjectDestructuring (token, is_const);
+		}
+		else if (isType (token, TOKEN_COMMA)
+				 || isType (token, TOKEN_DOTS))
+			in_left_side = true;
+		else if (in_left_side && isType (token, TOKEN_IDENTIFIER))
+		{
+			in_left_side = false;
+			makeJsTag (token, is_const ? JSTAG_CONSTANT : JSTAG_VARIABLE, NULL, NULL);
+		}
+		else if (isType (token, TOKEN_EQUAL_SIGN))
+		{
+			in_left_side = false;
+			/* TODO: SKIP */
+		}
+		else
+			in_left_side = false;
+	}
+}
+
+static void parseObjectDestructuring (tokenInfo *const token, bool is_const)
+{
+	tokenInfo *const name = newToken ();
+
+	/*
+	 * let { k0: v0, k1: v1 = 0, v3 };
+	 *     |   |  ||   |  |    |
+	 *     ^...|..|^...|..|....^.....: start
+	 *     ....^..|....^..|..........: colon
+	 *     .......^.......^..........: emitted (made a tag for an id after colon)
+	 */
+	enum objDestructuringState {
+		OBJ_DESTRUCTURING_START,
+		OBJ_DESTRUCTURING_COLON,
+		OBJ_DESTRUCTURING_EMITTED,
+	} state = OBJ_DESTRUCTURING_START;
+
+	while (! isType (token, TOKEN_EOF))
+	{
+		readToken (token);
+		if (isType (token, TOKEN_OPEN_CURLY))
+		{
+			parseObjectDestructuring (token, is_const);
+			if (state == OBJ_DESTRUCTURING_COLON)
+				state = OBJ_DESTRUCTURING_EMITTED;
+		}
+		else if (isType (token, TOKEN_CLOSE_CURLY))
+		{
+			if (!vStringIsEmpty(name->string))
+				makeJsTag (name, is_const ? JSTAG_CONSTANT : JSTAG_VARIABLE, NULL, NULL);
+			break;
+		}
+		else if (isType (token, TOKEN_OPEN_SQUARE))
+		{
+			parseArrayDestructuring (token, is_const);
+			if (state == OBJ_DESTRUCTURING_COLON)
+				state = OBJ_DESTRUCTURING_EMITTED;
+		}
+		else if (isType (token, TOKEN_IDENTIFIER))
+		{
+			if (state == OBJ_DESTRUCTURING_COLON)
+			{
+				makeJsTag (token, is_const ? JSTAG_CONSTANT : JSTAG_VARIABLE, NULL, NULL);
+				state = OBJ_DESTRUCTURING_EMITTED;
+			}
+			else if (state == OBJ_DESTRUCTURING_START
+					 && vStringIsEmpty(name->string))
+				copyToken(name, token, true);
+		}
+		else if (isType (token, TOKEN_COMMA))
+		{
+			if (!vStringIsEmpty(name->string))
+			{
+				makeJsTag (name, is_const ? JSTAG_CONSTANT : JSTAG_VARIABLE, NULL, NULL);
+				vStringClear (name->string);
+			}
+			state = OBJ_DESTRUCTURING_START;
+		}
+		else if (isType (token, TOKEN_COLON))
+		{
+			vStringClear (name->string);
+			state = OBJ_DESTRUCTURING_COLON;
+		}
+		else
+		{
+			if (state == OBJ_DESTRUCTURING_COLON)
+				state = OBJ_DESTRUCTURING_EMITTED;
+		}
+	}
+
+	deleteToken (name);
+}
+
 static bool parseStatement (tokenInfo *const token, bool is_inside_class)
 {
 	TRACE_ENTER_TEXT("is_inside_class: %s", is_inside_class? "yes": "no");
@@ -2322,6 +2437,14 @@ static bool parseStatement (tokenInfo *const token, bool is_inside_class)
 			is_global = true;
 		}
 		readToken(token);
+
+		if (is_global)
+		{
+			if (isType (token, TOKEN_OPEN_CURLY))
+				parseObjectDestructuring (token, is_const);
+			else if (isType (token, TOKEN_OPEN_SQUARE))
+				parseArrayDestructuring (token, is_const);
+		}
 	}
 
 nextVar:
@@ -2530,7 +2653,8 @@ static bool parseStatement (tokenInfo *const token, bool is_inside_class)
 			 * Handles this syntax:
 			 *	   var g_var2;
 			 */
-			indexForName = makeJsTag (name, is_const ? JSTAG_CONSTANT : JSTAG_VARIABLE, NULL, NULL);
+			if (! vStringIsEmpty (name->string))
+				indexForName = makeJsTag (name, is_const ? JSTAG_CONSTANT : JSTAG_VARIABLE, NULL, NULL);
 		}
 		/*
 		 * Statement has ended.
@@ -2749,7 +2873,8 @@ static bool parseStatement (tokenInfo *const token, bool is_inside_class)
 			}
 		}
 		else if (! isType (token, TOKEN_KEYWORD) &&
-				 token->nestLevel == 0 && is_global )
+				 token->nestLevel == 0 && is_global &&
+				 (! vStringIsEmpty (name->string)))
 		{
 			/*
 			 * Only create variables for global scope