discover custom template functions from Go source

Scans Go source files in the workspace for template.FuncMap definitions
and extracts function names to prevent false 'function undefined' errors
when analyzing templates that use custom functions.

On LSP initialize, the server now walks the workspace looking for Go files
with template.FuncMap composite literals, extracts the function names as
keys, and registers them with the analyzer. This allows templates to use
project-specific functions like 'lower', 'dict', 'localtime' etc without
triggering spurious errors.

Author: Jason-Abbott

.beans/gozer-3cy0--custom-template-function-discovery-via-go-ast-scan.md

@@ -0,0 +1,20 @@
+---
+# gozer-3cy0
+title: Custom Template Function Discovery via Go AST Scanning
+status: completed
+type: feature
+priority: normal
+created_at: 2026-01-18T20:00:15Z
+updated_at: 2026-01-18T20:03:56Z
+---
+
+Automatically discover custom template functions from Go source code to prevent false 'function undefined' errors.
+
+## Checklist
+
+- [x] Create `gota/analyzer/funcmap_scanner.go` with AST scanning logic
+- [x] Modify `gota/analyzer/analyzer.go` to merge custom functions with builtins
+- [x] Modify `gota/gota.go` to add custom function API
+- [x] Modify `gozer/cmd/go-template-lsp/main.go` to scan on initialize
+- [x] Add tests for funcmap scanner
+- [x] Run tests in both repos to verify

cmd/go-template-lsp/main.go

@@ -269,6 +269,19 @@ func processDiagnosticNotification(storage *workspaceStore, rootPathNotification
 
 	rootPath = uriToFilePath(rootPath)
 
+	// Scan for custom template functions defined in Go source files
+	customFuncs, err := gota.ScanWorkspaceForFuncMap(rootPath)
+	if err != nil {
+		slog.Warn("failed to scan for custom template functions", slog.String("error", err.Error()))
+	} else if len(customFuncs) > 0 {
+		gota.SetWorkspaceCustomFunctions(customFuncs)
+		funcNames := make([]string, 0, len(customFuncs))
+		for name := range customFuncs {
+			funcNames = append(funcNames, name)
+		}
+		slog.Info("discovered custom template functions", slog.Any("functions", funcNames))
+	}
+
 	storage.RootPath = rootPath
 	storage.RawFiles = gota.OpenProjectFiles(rootPath, TargetFileExtensions)
 	storage.RawFiles = convertKeysFromFilePathToUri(storage.RawFiles)

go.mod

@@ -4,4 +4,4 @@ go 1.25.6
 
 require github.com/yayolande/gota v0.8.4
 
-replace github.com/yayolande/gota => github.com/STR-Consulting/gota v0.8.4
+replace github.com/yayolande/gota => github.com/STR-Consulting/gota v0.8.5-0.20260118200612-37a5e41994a8

go.sum

@@ -1,5 +1,5 @@
-github.com/STR-Consulting/gota v0.8.4 h1:0eKo813kXDf87/d1kPsebNPd+K6fP4X9qB682XoFnlc=
-github.com/STR-Consulting/gota v0.8.4/go.mod h1:5kQtkYEDAKwdjlGKNuNGzs0mCJyUmkjCc2mj6Jeaq/I=
+github.com/STR-Consulting/gota v0.8.5-0.20260118200612-37a5e41994a8 h1:P//3nE1NoG+JoWf+JWI46P8p8ljHopDDcJ0OS4QzOBY=
+github.com/STR-Consulting/gota v0.8.5-0.20260118200612-37a5e41994a8/go.mod h1:5kQtkYEDAKwdjlGKNuNGzs0mCJyUmkjCc2mj6Jeaq/I=
 golang.org/x/mod v0.23.0 h1:Zb7khfcRGKk+kqfxFaP5tZqCnDZMjC5VtUBs87Hr6QM=
 golang.org/x/mod v0.23.0/go.mod h1:6SkKJ3Xj0I0BrPOZoBy3bdMptDDU9oJrpohJ3eWZ1fY=
 golang.org/x/sync v0.11.0 h1:GGz8+XQP4FvTTrjZPzNKTMFtSXH80RAzG+5ghFPgK9w=

zed-ext/extension.toml

@@ -1,6 +1,6 @@
 id = "go-template-lsp"
 name = "Go Template LSP"
-version = "0.2.2"
+version = "0.3.0"
 schema_version = 1
 authors = ["Jason Abbott", "Jason Staten", "yayolande", "Nikita Galaiko", "Mahmud Ridwan"]
 description = "Go template support with LSP (hover, diagnostics, go-to-definition)"