fix(lsp): filter completion candidates based on completeopt (#30945)

2 files changed, 287 insertions, 5 deletions

diff --git a/runtime/lua/vim/lsp/completion.lua b/runtime/lua/vim/lsp/completion.lua
index 10086fa49e..92bc110a97 100644
--- a/runtime/lua/vim/lsp/completion.lua
+++ b/runtime/lua/vim/lsp/completion.lua
@@ -220,6 +220,20 @@ local function get_doc(item)
   return ''
 end
 
+---@param value string
+---@param prefix string
+---@return boolean
+local function match_item_by_value(value, prefix)
+  if vim.o.completeopt:find('fuzzy') ~= nil then
+    return next(vim.fn.matchfuzzy({ value }, prefix)) ~= nil
+  end
+
+  if vim.o.ignorecase and (not vim.o.smartcase or not prefix:find('%u')) then
+    return vim.startswith(value:lower(), prefix:lower())
+  end
+  return vim.startswith(value, prefix)
+end
+
 --- Turns the result of a `textDocument/completion` request into vim-compatible
 --- |complete-items|.
 ---
@@ -244,8 +258,16 @@ function M._lsp_to_complete_items(result, prefix, client_id)
   else
     ---@param item lsp.CompletionItem
     matches = function(item)
-      local text = item.filterText or item.label
-      return next(vim.fn.matchfuzzy({ text }, prefix)) ~= nil
+      if item.filterText then
+        return match_item_by_value(item.filterText, prefix)
+      end
+
+      if item.textEdit then
+        -- server took care of filtering
+        return true
+      end
+
+      return match_item_by_value(item.label, prefix)
     end
   end
 
diff --git a/test/functional/plugin/lsp/completion_spec.lua b/test/functional/plugin/lsp/completion_spec.lua
index ec2f88ec32..39b6ddc105 100644
--- a/test/functional/plugin/lsp/completion_spec.lua
+++ b/test/functional/plugin/lsp/completion_spec.lua
@@ -134,10 +134,14 @@ describe('vim.lsp.completion: item conversion', function()
     eq(expected, result)
   end)
 
-  it('filters on label if filterText is missing', function()
+  it('does not filter if there is a textEdit', function()
+    local range0 = {
+      start = { line = 0, character = 0 },
+      ['end'] = { line = 0, character = 0 },
+    }
     local completion_list = {
-      { label = 'foo' },
-      { label = 'bar' },
+      { label = 'foo', textEdit = { newText = 'foo', range = range0 } },
+      { label = 'bar', textEdit = { newText = 'bar', range = range0 } },
     }
     local result = complete('fo|', completion_list)
     local expected = {
@@ -145,6 +149,10 @@ describe('vim.lsp.completion: item conversion', function()
         abbr = 'foo',
         word = 'foo',
       },
+      {
+        abbr = 'bar',
+        word = 'bar',
+      },
     }
     result = vim.tbl_map(function(x)
       return {
@@ -152,9 +160,261 @@ describe('vim.lsp.completion: item conversion', function()
         word = x.word,
       }
     end, result.items)
+    local sorter = function(a, b)
+      return a.word > b.word
+    end
+    table.sort(expected, sorter)
+    table.sort(result, sorter)
     eq(expected, result)
   end)
 
+  ---@param prefix string
+  ---@param items lsp.CompletionItem[]
+  ---@param expected table[]
+  local assert_completion_matches = function(prefix, items, expected)
+    local result = complete(prefix .. '|', items)
+    result = vim.tbl_map(function(x)
+      return {
+        abbr = x.abbr,
+        word = x.word,
+      }
+    end, result.items)
+    local sorter = function(a, b)
+      return a.word > b.word
+    end
+    table.sort(expected, sorter)
+    table.sort(result, sorter)
+    eq(expected, result)
+  end
+
+  describe('when completeopt has fuzzy matching enabled', function()
+    before_each(function()
+      exec_lua(function()
+        vim.opt.completeopt:append('fuzzy')
+      end)
+    end)
+    after_each(function()
+      exec_lua(function()
+        vim.opt.completeopt:remove('fuzzy')
+      end)
+    end)
+
+    it('fuzzy matches on filterText', function()
+      assert_completion_matches('fo', {
+        { label = '?.foo', filterText = 'foo' },
+        { label = 'faz other', filterText = 'faz other' },
+        { label = 'bar', filterText = 'bar' },
+      }, {
+        {
+          abbr = 'faz other',
+          word = 'faz other',
+        },
+        {
+          abbr = '?.foo',
+          word = '?.foo',
+        },
+      })
+    end)
+
+    it('fuzzy matches on label when filterText is missing', function()
+      assert_completion_matches('fo', {
+        { label = 'foo' },
+        { label = 'faz other' },
+        { label = 'bar' },
+      }, {
+        {
+          abbr = 'faz other',
+          word = 'faz other',
+        },
+        {
+          abbr = 'foo',
+          word = 'foo',
+        },
+      })
+    end)
+  end)
+
+  describe('when smartcase is enabled', function()
+    before_each(function()
+      exec_lua(function()
+        vim.opt.smartcase = true
+      end)
+    end)
+    after_each(function()
+      exec_lua(function()
+        vim.opt.smartcase = false
+      end)
+    end)
+
+    it('matches filterText case sensitively', function()
+      assert_completion_matches('Fo', {
+        { label = 'foo', filterText = 'foo' },
+        { label = '?.Foo', filterText = 'Foo' },
+        { label = 'Faz other', filterText = 'Faz other' },
+        { label = 'faz other', filterText = 'faz other' },
+        { label = 'bar', filterText = 'bar' },
+      }, {
+        {
+          abbr = '?.Foo',
+          word = '?.Foo',
+        },
+      })
+    end)
+
+    it('matches label case sensitively when filterText is missing', function()
+      assert_completion_matches('Fo', {
+        { label = 'foo' },
+        { label = 'Foo' },
+        { label = 'Faz other' },
+        { label = 'faz other' },
+        { label = 'bar' },
+      }, {
+        {
+          abbr = 'Foo',
+          word = 'Foo',
+        },
+      })
+    end)
+
+    describe('when ignorecase is enabled', function()
+      before_each(function()
+        exec_lua(function()
+          vim.opt.ignorecase = true
+        end)
+      end)
+      after_each(function()
+        exec_lua(function()
+          vim.opt.ignorecase = false
+        end)
+      end)
+
+      it('matches filterText case insensitively if prefix is lowercase', function()
+        assert_completion_matches('fo', {
+          { label = '?.foo', filterText = 'foo' },
+          { label = '?.Foo', filterText = 'Foo' },
+          { label = 'Faz other', filterText = 'Faz other' },
+          { label = 'faz other', filterText = 'faz other' },
+          { label = 'bar', filterText = 'bar' },
+        }, {
+          {
+            abbr = '?.Foo',
+            word = '?.Foo',
+          },
+          {
+            abbr = '?.foo',
+            word = '?.foo',
+          },
+        })
+      end)
+
+      it(
+        'matches label case insensitively if prefix is lowercase and filterText is missing',
+        function()
+          assert_completion_matches('fo', {
+            { label = 'foo' },
+            { label = 'Foo' },
+            { label = 'Faz other' },
+            { label = 'faz other' },
+            { label = 'bar' },
+          }, {
+            {
+              abbr = 'Foo',
+              word = 'Foo',
+            },
+            {
+              abbr = 'foo',
+              word = 'foo',
+            },
+          })
+        end
+      )
+
+      it('matches filterText case sensitively if prefix has uppercase letters', function()
+        assert_completion_matches('Fo', {
+          { label = 'foo', filterText = 'foo' },
+          { label = '?.Foo', filterText = 'Foo' },
+          { label = 'Faz other', filterText = 'Faz other' },
+          { label = 'faz other', filterText = 'faz other' },
+          { label = 'bar', filterText = 'bar' },
+        }, {
+          {
+            abbr = '?.Foo',
+            word = '?.Foo',
+          },
+        })
+      end)
+
+      it(
+        'matches label case sensitively if prefix has uppercase letters and filterText is missing',
+        function()
+          assert_completion_matches('Fo', {
+            { label = 'foo' },
+            { label = 'Foo' },
+            { label = 'Faz other' },
+            { label = 'faz other' },
+            { label = 'bar' },
+          }, {
+            {
+              abbr = 'Foo',
+              word = 'Foo',
+            },
+          })
+        end
+      )
+    end)
+  end)
+
+  describe('when ignorecase is enabled', function()
+    before_each(function()
+      exec_lua(function()
+        vim.opt.ignorecase = true
+      end)
+    end)
+    after_each(function()
+      exec_lua(function()
+        vim.opt.ignorecase = false
+      end)
+    end)
+
+    it('matches filterText case insensitively', function()
+      assert_completion_matches('Fo', {
+        { label = '?.foo', filterText = 'foo' },
+        { label = '?.Foo', filterText = 'Foo' },
+        { label = 'Faz other', filterText = 'Faz other' },
+        { label = 'faz other', filterText = 'faz other' },
+        { label = 'bar', filterText = 'bar' },
+      }, {
+        {
+          abbr = '?.Foo',
+          word = '?.Foo',
+        },
+        {
+          abbr = '?.foo',
+          word = '?.foo',
+        },
+      })
+    end)
+
+    it('matches label case insensitively when filterText is missing', function()
+      assert_completion_matches('Fo', {
+        { label = 'foo' },
+        { label = 'Foo' },
+        { label = 'Faz other' },
+        { label = 'faz other' },
+        { label = 'bar' },
+      }, {
+        {
+          abbr = 'Foo',
+          word = 'Foo',
+        },
+        {
+          abbr = 'foo',
+          word = 'foo',
+        },
+      })
+    end)
+  end)
+
   it('works on non word prefix', function()
     local completion_list = {
       { label = ' foo', insertText = '->foo' },