fix(graphql-language-service): wrap list input values in brackets on autocomplete

Completing an enum or boolean value for a list-typed argument or input
field (e.g. `[Episode]`) inserted a bare `JEDI`, which isn't valid there.
The online parser already unwraps one list level once the caret is inside
a `[ ]`, so the remaining list depth tells us how many brackets to add —
this also covers nested lists like `[[Episode]]`. Values typed inside an
existing list literal, single (non-list) values and variables are left
untouched.

Closes #587

Author: DukeDeSouth

.changeset/wrap-list-input-values.md

@@ -0,0 +1,7 @@
+---
+'graphql-language-service': patch
+---
+
+Wrap autocompleted list input values in square brackets
+
+When you complete an enum or boolean value for a list-typed argument or input field (e.g. `[Episode]`), the suggestion now inserts `[JEDI]` instead of a bare `JEDI`, which produced an invalid query. Values completed inside an existing list literal, and non-list values, are left as they were.

packages/graphql-language-service/src/interface/__tests__/getAutocompleteSuggestions.test.ts

@@ -1023,3 +1023,96 @@ describe('getAutocompleteSuggestions', () => {
       ]));
   });
 });
+
+describe('getAutocompleteSuggestions - list input values (#587)', () => {
+  const listSchema = buildSchema(`
+    enum Episode { NEWHOPE EMPIRE JEDI }
+    input FilterInput {
+      episodes: [Episode]
+      one: Episode
+    }
+    type Query {
+      listEnum(values: [Episode]): String
+      listEnumNonNull(values: [Episode!]!): String
+      listBool(flags: [Boolean]): String
+      singleEnum(value: Episode): String
+      nestedList(values: [[Episode]]): String
+      nested(input: FilterInput): String
+    }
+  `);
+
+  function valueSuggestions(query: string, label: string) {
+    const caret = query.indexOf('|');
+    const text = query.replace('|', '');
+    const before = text.slice(0, caret);
+    const line = before.split('\n').length - 1;
+    const character = before.length - (before.lastIndexOf('\n') + 1);
+    return getAutocompleteSuggestions(
+      listSchema,
+      text,
+      new Position(line, character),
+    )
+      .filter(s => s.label === label)
+      .map(s => ({ label: s.label, insertText: s.insertText }));
+  }
+
+  it('wraps an enum value in brackets at a list argument value position', () => {
+    expect(valueSuggestions('{ listEnum(values: |) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: '[JEDI]' },
+    ]);
+  });
+
+  it('wraps an enum value for a non-null list of non-null items', () => {
+    expect(valueSuggestions('{ listEnumNonNull(values: |) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: '[JEDI]' },
+    ]);
+  });
+
+  it('wraps a boolean value in brackets at a list argument value position', () => {
+    expect(valueSuggestions('{ listBool(flags: |) }', 'true')).toEqual([
+      { label: 'true', insertText: '[true]' },
+    ]);
+  });
+
+  it('wraps an enum value at a list input-object field value position', () => {
+    expect(
+      valueSuggestions('{ nested(input: { episodes: | }) }', 'JEDI'),
+    ).toEqual([{ label: 'JEDI', insertText: '[JEDI]' }]);
+  });
+
+  it('does not wrap when the cursor is already inside the list literal', () => {
+    expect(valueSuggestions('{ listEnum(values: [|]) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: undefined },
+    ]);
+  });
+
+  it('does not wrap a non-list (single) enum argument value', () => {
+    expect(valueSuggestions('{ singleEnum(value: |) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: undefined },
+    ]);
+  });
+
+  it('does not wrap a non-list (single) input-object enum field value', () => {
+    expect(valueSuggestions('{ nested(input: { one: | }) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: undefined },
+    ]);
+  });
+
+  it('wraps a nested list value with the matching number of brackets', () => {
+    expect(valueSuggestions('{ nestedList(values: |) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: '[[JEDI]]' },
+    ]);
+  });
+
+  it('wraps once when inside the outer bracket of a nested list', () => {
+    expect(valueSuggestions('{ nestedList(values: [|]) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: '[JEDI]' },
+    ]);
+  });
+
+  it('does not wrap when inside both brackets of a nested list', () => {
+    expect(valueSuggestions('{ nestedList(values: [[|]]) }', 'JEDI')).toEqual([
+      { label: 'JEDI', insertText: undefined },
+    ]);
+  });
+});

packages/graphql-language-service/src/interface/getAutocompleteSuggestions.ts

@@ -39,6 +39,8 @@ import {
   assertAbstractType,
   doTypesOverlap,
   getNamedType,
+  getNullableType,
+  isListType,
   isAbstractType,
   isCompositeType,
   isInputType,
@@ -575,6 +577,25 @@ function getSuggestionsForInputValues(
 ): Array<CompletionItem> {
   const namedInputType = getNamedType(typeInfo.inputType!);
 
+  // When the value position expects a list (e.g. `[Episode]`), a bare literal
+  // like `JEDI` is invalid — it must be wrapped as `[JEDI]`. The online parser
+  // unwraps one list level each time the cursor moves inside a list literal
+  // (`[ | ]`), so the number of list wrappers still present here is exactly how
+  // many brackets we need to add (handles nested lists like `[[Episode]]` too).
+  // Variable completions ($var) reference the whole list and must not be wrapped.
+  let listDepth = 0;
+  let unwrapped: GraphQLType | null | undefined = getNullableType(
+    typeInfo.inputType,
+  );
+  while (unwrapped && isListType(unwrapped)) {
+    listDepth++;
+    unwrapped = getNullableType(unwrapped.ofType);
+  }
+  const wrap = (literal: string): string | undefined =>
+    listDepth > 0
+      ? '['.repeat(listDepth) + literal + ']'.repeat(listDepth)
+      : undefined;
+
   const queryVariables: CompletionItem[] = getVariableCompletions(
     queryText,
     schema,
@@ -588,6 +609,7 @@ function getSuggestionsForInputValues(
       values
         .map<CompletionItem>((value: GraphQLEnumValue) => ({
           label: value.name,
+          insertText: wrap(value.name),
           detail: String(namedInputType),
           documentation: value.description ?? undefined,
           deprecated: Boolean(value.deprecationReason),
@@ -605,13 +627,15 @@ function getSuggestionsForInputValues(
       queryVariables.concat([
         {
           label: 'true',
+          insertText: wrap('true'),
           detail: String(GraphQLBoolean),
           documentation: 'Not false.',
           kind: CompletionItemKind.Variable,
           type: GraphQLBoolean,
         },
         {
           label: 'false',
+          insertText: wrap('false'),
           detail: String(GraphQLBoolean),
           documentation: 'Not true.',
           kind: CompletionItemKind.Variable,