Support import.meta and import.meta.* (#5319)

Co-authored-by: Geoffrey Booth <[email protected]>

Author: aurium

.github/workflows/continuous-integration.yml

@@ -2,8 +2,7 @@
 
 name: Build and Test
 
-on:
-  push
+on: [push, pull_request]
 
 jobs:
   ci:

lib/coffeescript/grammar.js

@@ -34,6 +34,9 @@ o = (patternString, action, options) ->
   patternString = patternString.replace /\s{2,}/g, ' '
   patternCount = patternString.split(' ').length
   if action
+    # This code block does string replacements in the generated `parser.js`
+    # file, replacing the calls to the `LOC` function and other strings as
+    # listed below.
     action = if match = unwrap.exec action then match[1] else "(#{action}())"
 
     # All runtime functions we need are defined on `yy`
@@ -47,8 +50,33 @@ o = (patternString, action, options) ->
     getAddDataToNodeFunctionString = (first, last, forceUpdateLocation = yes) ->
       "yy.addDataToNode(yy, @#{first}, #{if first[0] is '$' then '$$' else '$'}#{first}, #{if last then "@#{last}, #{if last[0] is '$' then '$$' else '$'}#{last}" else 'null, null'}, #{if forceUpdateLocation then 'true' else 'false'})"
 
+    # This code replaces the calls to `LOC` with the `yy.addDataToNode` string
+    # defined above. The `LOC` function, when used below in the grammar rules,
+    # is used to make sure that newly created node class objects get correct
+    # location data assigned to them. By default, the grammar will assign the
+    # location data spanned by *all* of the tokens on the left (e.g. a string
+    # such as `'Body TERMINATOR Line'`) to the “top-level” node returned by 
+    # the grammar rule (the function on the right). But for “inner” node class
+    # objects created by grammar rules, they won’t get correct location data
+    # assigned to them without adding `LOC`.
+    
+    # For example, consider the grammar rule `'NEW_TARGET . Property'`, which
+    # is handled by a function that returns
+    # `new MetaProperty LOC(1)(new IdentifierLiteral $1), LOC(3)(new Access $3)`.
+    # The `1` in `LOC(1)` refers to the first token (`NEW_TARGET`) and the `3`
+    # in `LOC(3)` refers to the third token (`Property`). In order for the
+    # `new IdentifierLiteral` to get assigned the location data corresponding
+    # to `new` in the source code, we use
+    # `LOC(1)(new IdentifierLiteral ...)` to mean “assign the location data of
+    # the *first* token of this grammar rule (`NEW_TARGET`) to this
+    # `new IdentifierLiteral`”. The `LOC(3)` means “assign the location data of
+    # the *third* token of this grammar rule (`Property`) to this
+    # `new Access`”.
     returnsLoc = /^LOC/.test action
     action = action.replace /LOC\(([0-9]*)\)/g, getAddDataToNodeFunctionString('$1')
+    # A call to `LOC` with two arguments, e.g. `LOC(2,4)`, sets the location
+    # data for the generated node on both of the referenced tokens  (the second
+    # and fourth in this example).
     action = action.replace /LOC\(([0-9]*),\s*([0-9]*)\)/g, getAddDataToNodeFunctionString('$1', '$2')
     performActionFunctionString = "$$ = #{getAddDataToNodeFunctionString(1, patternCount, not returnsLoc)}(#{action});"
   else
@@ -396,6 +424,7 @@ grammar =
   # A "meta-property" access e.g. `new.target`
   MetaProperty: [
     o 'NEW_TARGET . Property',                  -> new MetaProperty LOC(1)(new IdentifierLiteral $1), LOC(3)(new Access $3)
+    o 'IMPORT_META . Property',                 -> new MetaProperty LOC(1)(new IdentifierLiteral $1), LOC(3)(new Access $3)
   ]
 
   # The general group of accessors into an object, by property, by prototype

lib/coffeescript/lexer.js

@@ -214,6 +214,9 @@ exports.Lexer = class Lexer
         without parentheses", prev[2]
       else if prev[0] is '.' and @tokens.length > 1 and (prevprev = @tokens[@tokens.length - 2])[0] is 'UNARY' and prevprev[1] is 'new'
         prevprev[0] = 'NEW_TARGET'
+      else if prev[0] is '.' and @tokens.length > 1 and (prevprev = @tokens[@tokens.length - 2])[0] is 'IMPORT' and prevprev[1] is 'import'
+        @seenImport = no
+        prevprev[0] = 'IMPORT_META'
       else if @tokens.length > 2
         prevprev = @tokens[@tokens.length - 2]
         if prev[0] in ['@', 'THIS'] and prevprev and prevprev.spaced and

lib/coffeescript/nodes.js

@@ -1576,6 +1576,9 @@ exports.MetaProperty = class MetaProperty extends Base
           @error "new.target can only occur inside functions"
       else
         @error "the only valid meta property for new is new.target"
+    else if @meta.value is 'import'
+      unless @property instanceof Access and @property.name.value is 'meta'
+        @error "the only valid meta property for import is import.meta"
 
   compileNode: (o) ->
     @checkValid o

lib/coffeescript/parser.js

@@ -4041,7 +4041,7 @@ test "AST as expected for If node", ->
         inverted: no
       ]
 
-test "AST as expected for MetaProperty node", ->
+test "AST as expected for `new.target` MetaProperty node", ->
   testExpression '''
     -> new.target
   ''',
@@ -4074,6 +4074,25 @@ test "AST as expected for MetaProperty node", ->
           computed: no
       ]
 
+test "AST as expected for `import.meta` MetaProperty node", ->
+  testExpression '''
+    import.meta
+  ''',
+    type: 'MetaProperty'
+    meta: ID 'import'
+    property: ID 'meta'
+
+  testExpression '''
+    import.meta.name
+  ''',
+    type: 'MemberExpression'
+    object:
+      type: 'MetaProperty'
+      meta: ID 'import'
+      property: ID 'meta'
+    property: ID 'name'
+    computed: no
+
 test "AST as expected for dynamic import", ->
   testExpression '''
     import('a')

src/grammar.coffee

@@ -6006,7 +6006,7 @@ test "AST as expected for While node", ->
         line: 3
         column: 5
 
-test "AST location data as expected for MetaProperty node", ->
+test "AST location data as expected for `new.target` MetaProperty node", ->
   testAstLocationData '''
     -> new.target
   ''',
@@ -6058,6 +6058,44 @@ test "AST location data as expected for MetaProperty node", ->
         line: 1
         column: 13
 
+test "AST location data as expected for `import.meta` MetaProperty node", ->
+  testAstLocationData '''
+    import.meta
+  ''',
+    type: 'MetaProperty'
+    meta:
+      start: 0
+      end: 6
+      range: [0, 6]
+      loc:
+        start:
+          line: 1
+          column: 0
+        end:
+          line: 1
+          column: 6
+    property:
+      start: 7
+      end: 11
+      range: [7, 11]
+      loc:
+        start:
+          line: 1
+          column: 7
+        end:
+          line: 1
+          column: 11
+    start: 0
+    end: 11
+    range: [0, 11]
+    loc:
+      start:
+        line: 1
+        column: 0
+      end:
+        line: 1
+        column: 11
+
 test "AST location data as expected for For node", ->
   testAstLocationData 'for x, i in arr when x? then return',
     type: 'For'