diagnostic `missing-return-value`

1 files changed, 62 insertions, 0 deletions

diff --git a/script/core/diagnostics/missing-return-value.lua b/script/core/diagnostics/missing-return-value.lua
new file mode 100644
index 00000000..491475c7
--- /dev/null
+++ b/script/core/diagnostics/missing-return-value.lua
@@ -0,0 +1,62 @@
+local files  = require 'files'
+local guide  = require 'parser.guide'
+local vm     = require 'vm'
+local lang   = require 'language'
+
+local function hasDocReturn(func)
+    if not func.bindDocs then
+        return false
+    end
+    for _, doc in ipairs(func.bindDocs) do
+        if doc.type == 'doc.return' then
+            return true
+        end
+    end
+    return false
+end
+
+return function (uri, callback)
+    local state = files.getState(uri)
+    if not state then
+        return
+    end
+
+    guide.eachSourceType(state.ast, 'function', function (source)
+        if not hasDocReturn(source) then
+            return
+        end
+        local min = vm.countReturnsOfFunction(source)
+        if min == 0 then
+            return
+        end
+        local returns = source.returns
+        if not returns then
+            return
+        end
+        for _, ret in ipairs(returns) do
+            local rmin, rmax = vm.countList(ret)
+            if rmax < min then
+                if rmin == rmax then
+                    callback {
+                        start   = ret.start,
+                        finish  = ret.start + #'return',
+                        message = lang.script('DIAG_MISSING_RETURN_VALUE', {
+                            min  = min,
+                            rmax = rmax,
+                        }),
+                    }
+                else
+                    callback {
+                        start   = ret.start,
+                        finish  = ret.start + #'return',
+                        message = lang.script('DIAG_MISSING_RETURN_VALUE', {
+                            min  = min,
+                            rmin = rmin,
+                            rmax = rmax,
+                        }),
+                    }
+                end
+            end
+        end
+    end)
+end