fix: allow imports after the first declaration for resilience

tree-sitter · May 4, 2024 · fbd2cd5 · fbd2cd5
1 parent 50a04bf
commit fbd2cd5
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Showing 4 changed files with 68 additions and 28 deletions.
diff --git a/grammar/module.js b/grammar/module.js
@@ -28,7 +28,7 @@ module.exports = {
   namespace: _ => choice('pattern', 'type'),
 
   _child_type: $ => seq(field('namespace', 'type'), field('type', $._tyconids)),
- 
+
   _child: $ => choice(
     alias($._child_type, $.associated_type),
     $._qname,
@@ -96,8 +96,18 @@ module.exports = {
 
   /**
    * Using `semi` at the end instead of `semi_opt` increases parser size by a full megabyte!!
+   *
+   * This allows imports after the first declaration to prevent the tree from jittering while typing an import:
+   *
+   * > import A
+   * > imp
+   * > import B
+   *
+   * The partially typed `imp` will be parsed as a `top_splice`, which forces `imports` to reduce after `import A`.
+   * The rest of the file will then be part of `declarations` and all following imports will be broken until the keyword
+   * has been completed.
    */
-  declarations: $ => seq(semis($, $.declaration), semi_opt($)),
+  declarations: $ => seq($.declaration, repeat(seq(semi($), choice($.declaration, $.import))), semi_opt($)),
 
   _body: $ => seq(
     choice($._cmd_layout_start, alias($._cmd_layout_start_explicit, '{')),

diff --git a/src/grammar.json b/src/grammar.json
@@ -6461,41 +6461,45 @@
       "type": "SEQ",
       "members": [
         {
-          "type": "SEQ",
-          "members": [
-            {
-              "type": "SYMBOL",
-              "name": "declaration"
-            },
-            {
-              "type": "REPEAT",
-              "content": {
-                "type": "SEQ",
+          "type": "SYMBOL",
+          "name": "declaration"
+        },
+        {
+          "type": "REPEAT",
+          "content": {
+            "type": "SEQ",
+            "members": [
+              {
+                "type": "CHOICE",
                 "members": [
                   {
-                    "type": "CHOICE",
-                    "members": [
-                      {
-                        "type": "REPEAT1",
-                        "content": {
-                          "type": "STRING",
-                          "value": ";"
-                        }
-                      },
-                      {
-                        "type": "SYMBOL",
-                        "name": "_cond_layout_semicolon"
-                      }
-                    ]
+                    "type": "REPEAT1",
+                    "content": {
+                      "type": "STRING",
+                      "value": ";"
+                    }
                   },
+                  {
+                    "type": "SYMBOL",
+                    "name": "_cond_layout_semicolon"
+                  }
+                ]
+              },
+              {
+                "type": "CHOICE",
+                "members": [
                   {
                     "type": "SYMBOL",
                     "name": "declaration"
+                  },
+                  {
+                    "type": "SYMBOL",
+                    "name": "import"
                   }
                 ]
               }
-            }
-          ]
+            ]
+          }
         },
         {
           "type": "CHOICE",

diff --git a/src/node-types.json b/src/node-types.json
@@ -1776,6 +1776,10 @@
         {
           "type": "declaration",
           "named": true
+        },
+        {
+          "type": "import",
+          "named": true
         }
       ]
     }

diff --git a/test/corpus/import.txt b/test/corpus/import.txt
@@ -483,3 +483,25 @@ import A (A (type A, A, ..))
               (name))
             (constructor)
             (all_names)))))))
+
+================================================================================
+import: partially typed import before the end of the block
+================================================================================
+
+import A
+impo
+import A
+
+--------------------------------------------------------------------------------
+
+(haskell
+  (imports
+    (import
+      (module
+        (module_id))))
+  (declarations
+    (top_splice
+      (variable))
+    (import
+      (module
+        (module_id)))))