From 5c187765b671cbafac2262d29942bafd511a8a4d Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Tue, 20 Feb 2024 17:14:39 -0600
Subject: [PATCH] Give useful error if probably missing I()

Fixes #1451
---
 R/tbl-sql.R                      | 22 +++++++++++++++++++---
 tests/testthat/_snaps/tbl-sql.md | 14 ++++++++++++++
 tests/testthat/test-tbl-sql.R    |  7 +++++++
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/R/tbl-sql.R b/R/tbl-sql.R
index fd93ccc9e..6aa61dc9c 100644
--- a/R/tbl-sql.R
+++ b/R/tbl-sql.R
@@ -17,13 +17,29 @@ tbl_sql <- function(subclass, src, from, ..., vars = NULL, check_from = TRUE) {
   # Can't use check_dots_used(), #1429
   check_character(vars, allow_null = TRUE)
 
-  from <- as_table_source(from, con = src$con)
-  vars <- vars %||% dbplyr_query_fields(src$con, from)
+  is_suspicious <- is_bare_string(from) && grepl(".", from, fixed = TRUE)
+  source <- as_table_source(from, con = src$con)
+
+  withCallingHandlers(
+    vars <- vars %||% dbplyr_query_fields(src$con, source),
+    error = function(err) {
+      if (!is_suspicious) return()
+
+      cli::cli_abort(
+        c(
+          "Failed to find table {source}.",
+          i = "Did you mean {.code from = I({.str {from}})}?"
+        ),
+        parent = err
+      )
+    }
+  )
+
 
   dplyr::make_tbl(
     c(subclass, "sql", "lazy"),
     src = src,
-    lazy_query = lazy_query_remote(from, vars)
+    lazy_query = lazy_query_remote(source, vars)
   )
 }
 
diff --git a/tests/testthat/_snaps/tbl-sql.md b/tests/testthat/_snaps/tbl-sql.md
index 7b9b38a82..c3b92694a 100644
--- a/tests/testthat/_snaps/tbl-sql.md
+++ b/tests/testthat/_snaps/tbl-sql.md
@@ -11,3 +11,17 @@
       2     2     2
       3     3     1
 
+# useful error if missing I()
+
+    Code
+      tbl(src_memdb(), "foo.bar")
+    Condition
+      Error in `tbl_sql()`:
+      ! Failed to find table `foo.bar`.
+      i Did you mean `from = I("foo.bar")`?
+      Caused by error in `db_query_fields.DBIConnection()`:
+      ! Can't query fields.
+      i Using SQL: SELECT * FROM `foo.bar` AS `q05` WHERE (0 = 1)
+      Caused by error:
+      ! no such table: foo.bar
+
diff --git a/tests/testthat/test-tbl-sql.R b/tests/testthat/test-tbl-sql.R
index 5177faaff..069a825eb 100644
--- a/tests/testthat/test-tbl-sql.R
+++ b/tests/testthat/test-tbl-sql.R
@@ -54,6 +54,13 @@ test_that("can distinguish 'schema.table' from 'schema'.'table'", {
   expect_equal(as.character(tbl_vars(df)), c("a", "b", "c"))
 })
 
+test_that("useful error if missing I()", {
+  expect_snapshot(
+    tbl(src_memdb(), "foo.bar"),
+    error = TRUE
+  )
+})
+
 # n_groups ----------------------------------------------------------------
 
 test_that("check basic group size implementation", {