fix(iterables): iterables are non-stateful

BREAKING CHANGE: iterables were stateful and one could only iterate over them once, refferential transparency could not be guaranteed and extra care had to be taken, caching their items using `[...iterable]`. Now iterables are not stateful anymore and can be reused and iterated over multiple times.
fink-lang · Oct 24, 2020 · 6738618 · 6738618
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commit 6738618
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diff --git a/src/js/async.fnk b/src/js/async.fnk
@@ -1,5 +1,7 @@
 babel_types = import '@babel/types'
-{isArrowFunctionExpression, isFunctionExpression, isForOfStatement} = babel_types
+{
+  isArrowFunctionExpression, isForOfStatement, isObjectMethod
+} = babel_types
 {set_props} = import '@fink/js-interop/reflect.fnk'
 
 
@@ -12,8 +14,12 @@ transform_async = fn path:
     isArrowFunctionExpression ?:
       set_props path.node, {async: true}
 
-    isFunctionExpression ?:
+    # generators for iterables
+    isObjectMethod ?:
       set_props path.node, {async: true}
+      match path.node:
+        {key: {property: {name: 'iterator'}}}:
+          set_props path.node.key.property, {name: 'asyncIterator'}
 
     isForOfStatement ?:
       set_props path.node, {await: true}

diff --git a/src/js/types.fnk b/src/js/types.fnk
@@ -10,7 +10,8 @@ babe_types = import '@babel/types'
   expressionStatement, functionExpression
   blockStatement, identifier, arrowFunctionExpression
   logicalExpression, binaryExpression, unaryExpression
-  doExpression, assignmentExpression, isIdentifier
+  doExpression, assignmentExpression, isIdentifier, objectExpression,
+  returnStatement, objectMethod, memberExpression
 } = babe_types
 
 
@@ -101,10 +102,29 @@ func = fn args, ...expressions:
     expr_block ...expressions
 
 
+symbol = fn symb:
+  memberExpression
+    identifier 'Symbol'
+    identifier symb
+
+
+computed = true
+async = true
+
+
 generator = fn name, args, ...statements:
   func_name = ident name
-  body = blockStatement statements
-  functionExpression func_name, args,  body, true
+
+  functionExpression func_name, args,
+    blockStatement list:
+      returnStatement
+        objectExpression list:
+          objectMethod
+            'method', (symbol 'iterator'), []
+            blockStatement list:
+              ...statements
+            computed
+            async
 
 
 for_of = fn [item, items], ...expressions:

diff --git a/src/lang/async/init.test.fnk.snap b/src/lang/async/init.test.fnk.snap
@@ -8,33 +8,38 @@ export const task3 = async (foo) => {
   const spam = await foo();
   return bar + 123;
 };
-export const a_gen = async function* unfold(ˆinitial_2) {
-  let ˆaccu_3 = 0;
+export const a_gen = function unfold(ˆinitial_2) {
+  return {
+    async *[Symbol.asyncIterator]() {
+      let ˆaccu_3 = 0;
 
-  while (true) {
-    const curr = ˆaccu_3;
+      while (true) {
+        const curr = ˆaccu_3;
 
-    let _do_result;
+        let _do_result;
 
-    ˆmatch_5: {
-      const ˆvalue_4 = shrub;
+        ˆmatch_5: {
+          const ˆvalue_4 = shrub;
 
-      if (ˆvalue_4 === spam) {
-        _do_result = await ni(curr);
-        break ˆmatch_5;
-      }
+          if (ˆvalue_4 === spam) {
+            _do_result = await ni(curr);
+            break ˆmatch_5;
+          }
 
-      {
-        _do_result = curr + 1;
-        break ˆmatch_5;
+          {
+            _do_result = curr + 1;
+            break ˆmatch_5;
+          }
+        }
+
+        const ˆresult_1 = _do_result;
+        _do_result = undefined;
+        yield ˆresult_1;
+        ˆaccu_3 = ˆresult_1;
       }
     }
 
-    const ˆresult_1 = _do_result;
-    _do_result = undefined;
-    yield ˆresult_1;
-    ˆaccu_3 = ˆresult_1;
-  }
+  };
 };
 await ni;"
 `;
@@ -48,15 +53,20 @@ exports[`await handles awaiting async iterables 1`] = `
   {
     let ˆpipe_result_3 = undefined;
 
-    _do_result2 = ˆpipe_result_3 = async function* unfold(ˆinitial_5) {
-      let ˆaccu_6 = 0;
+    _do_result2 = ˆpipe_result_3 = function unfold(ˆinitial_5) {
+      return {
+        async *[Symbol.asyncIterator]() {
+          let ˆaccu_6 = 0;
 
-      while (true) {
-        const cntr = ˆaccu_6;
-        const ˆresult_4 = (await cntr) + 1;
-        yield ˆresult_4;
-        ˆaccu_6 = ˆresult_4;
-      }
+          while (true) {
+            const cntr = ˆaccu_6;
+            const ˆresult_4 = (await cntr) + 1;
+            yield ˆresult_4;
+            ˆaccu_6 = ˆresult_4;
+          }
+        }
+
+      };
     }(ˆpipe_result_3);
   }
   const ˆitems_1 = _do_result2;

diff --git a/src/lang/call/pipe.test.fnk b/src/lang/call/pipe.test.fnk
@@ -13,13 +13,13 @@ describe 'pipe', fn:
           spam
           [...?]
 
-
         pipe [1, 2, 3]:
           map item: item * 2
       '
       to_match_snapshot
 
 
+
 describe 'small pipe |', fn:
   it 'pipes', fn:
     expect

diff --git a/src/lang/call/pipe.test.fnk.snap b/src/lang/call/pipe.test.fnk.snap
@@ -17,12 +17,17 @@ exports[`pipe compiles 1`] = `
 {
   let ˆpipe_result_2 = [1, 2, 3];
 
-  ˆpipe_result_2 = function* map(ˆitems_4) {
-    for (const ˆitem_3 of ˆitems_4) {
-      const item = ˆitem_3;
-      const ˆresult_5 = item * 2;
-      yield ˆresult_5;
-    }
+  ˆpipe_result_2 = function map(ˆitems_4) {
+    return {
+      *[Symbol.iterator]() {
+        for (const ˆitem_3 of ˆitems_4) {
+          const item = ˆitem_3;
+          const ˆresult_5 = item * 2;
+          yield ˆresult_5;
+        }
+      }
+
+    };
   }(ˆpipe_result_2);
 }"
 `;

diff --git a/src/lang/iterable/filter.test.fnk.snap b/src/lang/iterable/filter.test.fnk.snap
@@ -1,85 +1,120 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`filter async compiles 1`] = `
-"(async function* filter(ˆitems_2) {
-  for await (const ˆitem_1 of ˆitems_2) {
-    const item = ˆitem_1;
-    const ˆresult_3 = (await item) % 2 === 0;
-    if (ˆresult_3) yield ˆitem_1;
-  }
+"(function filter(ˆitems_2) {
+  return {
+    async *[Symbol.asyncIterator]() {
+      for await (const ˆitem_1 of ˆitems_2) {
+        const item = ˆitem_1;
+        const ˆresult_3 = (await item) % 2 === 0;
+        if (ˆresult_3) yield ˆitem_1;
+      }
+    }
+
+  };
 });"
 `;
 
 exports[`filter compiles 1`] = `
-"(function* filter(ˆitems_2) {
-  for (const ˆitem_1 of ˆitems_2) {
-    const item = ˆitem_1;
-    const ˆresult_3 = item % 2 === 0;
-    if (ˆresult_3) yield ˆitem_1;
-  }
+"(function filter(ˆitems_2) {
+  return {
+    *[Symbol.iterator]() {
+      for (const ˆitem_1 of ˆitems_2) {
+        const item = ˆitem_1;
+        const ˆresult_3 = item % 2 === 0;
+        if (ˆresult_3) yield ˆitem_1;
+      }
+    }
+
+  };
 });
 
-(function* filter(ˆitems_5) {
-  for (const ˆitem_4 of ˆitems_5) {
-    const [a, ...b] = ˆitem_4;
-    const a_alone = a(andis_empty(b));
-    const ˆresult_6 = a_alone;
-    if (ˆresult_6) yield ˆitem_4;
-  }
+(function filter(ˆitems_5) {
+  return {
+    *[Symbol.iterator]() {
+      for (const ˆitem_4 of ˆitems_5) {
+        const [a, ...b] = ˆitem_4;
+        const a_alone = a(andis_empty(b));
+        const ˆresult_6 = a_alone;
+        if (ˆresult_6) yield ˆitem_4;
+      }
+    }
+
+  };
 });
 
-(function* filter(ˆitems_9) {
-  for (const ˆitem_7 of ˆitems_9) {
-    let _do_result;
+(function filter(ˆitems_9) {
+  return {
+    *[Symbol.iterator]() {
+      for (const ˆitem_7 of ˆitems_9) {
+        let _do_result;
 
-    {
-      const [...ˆitems_8] = ˆitem_7;
-      _do_result = [ˆitems_8.slice(0, -1), ˆitems_8.slice(-1)];
+        {
+          const [...ˆitems_8] = ˆitem_7;
+          _do_result = [ˆitems_8.slice(0, -1), ˆitems_8.slice(-1)];
+        }
+        const [a, [b]] = _do_result;
+        _do_result = undefined;
+        const ˆresult_10 = b && is_empty(a);
+        if (ˆresult_10) yield ˆitem_7;
+      }
     }
-    const [a, [b]] = _do_result;
-    _do_result = undefined;
-    const ˆresult_10 = b && is_empty(a);
-    if (ˆresult_10) yield ˆitem_7;
-  }
+
+  };
 });"
 `;
 
 exports[`filter compiles with accu 1`] = `
-"(function* filter(ˆitems_3) {
-  let ˆaccu_2 = 0;
-
-  for (const ˆitem_1 of ˆitems_3) {
-    const item = ˆitem_1;
-    const cntr = ˆaccu_2;
-    const ˆresult_4 = item < 1 && cntr % 2 === 0;
-    if (ˆresult_4) yield ˆitem_1;
-    ˆaccu_2 = cntr + 1;
-  }
+"(function filter(ˆitems_3) {
+  return {
+    *[Symbol.iterator]() {
+      let ˆaccu_2 = 0;
+
+      for (const ˆitem_1 of ˆitems_3) {
+        const item = ˆitem_1;
+        const cntr = ˆaccu_2;
+        const ˆresult_4 = item < 1 && cntr % 2 === 0;
+        if (ˆresult_4) yield ˆitem_1;
+        ˆaccu_2 = cntr + 1;
+      }
+    }
+
+  };
 });"
 `;
 
 exports[`filter compiles with accu 2`] = `
-"(function* filter(ˆitems_3) {
-  let ˆaccu_2 = false;
-
-  for (const ˆitem_1 of ˆitems_3) {
-    const is_even = ˆaccu_2;
-    const ˆresult_4 = is_even;
-    if (ˆresult_4) yield ˆitem_1;
-    ˆaccu_2 = !is_even;
-  }
+"(function filter(ˆitems_3) {
+  return {
+    *[Symbol.iterator]() {
+      let ˆaccu_2 = false;
+
+      for (const ˆitem_1 of ˆitems_3) {
+        const is_even = ˆaccu_2;
+        const ˆresult_4 = is_even;
+        if (ˆresult_4) yield ˆitem_1;
+        ˆaccu_2 = !is_even;
+      }
+    }
+
+  };
 });"
 `;
 
 exports[`filter compiles with accu 3`] = `
-"(function* filter(ˆitems_3) {
-  let ˆaccu_2 = false;
-
-  for (const ˆitem_1 of ˆitems_3) {
-    const is_even = ˆaccu_2;
-    const ˆresult_4 = is_even;
-    if (ˆresult_4) yield ˆitem_1;
-    ˆaccu_2 = !is_even;
-  }
+"(function filter(ˆitems_3) {
+  return {
+    *[Symbol.iterator]() {
+      let ˆaccu_2 = false;
+
+      for (const ˆitem_1 of ˆitems_3) {
+        const is_even = ˆaccu_2;
+        const ˆresult_4 = is_even;
+        if (ˆresult_4) yield ˆitem_1;
+        ˆaccu_2 = !is_even;
+      }
+    }
+
+  };
 });"
 `;