(texera) 01/01: fix(BarChart): treat an empty categoryColumn as no category (px.bar color) (#6807)

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github-merge-queue[bot] pushed a commit to branch gh-readonly-queue/main/pr-6807-6495ebd84ab0dc7f4f6b1d4fbc09ff051f4cfd10
in repository https://gitbox.apache.org/repos/asf/texera.git

commit c24755c98e0d17b07712ee677ee9ddd7d33ccb68
Author: Kary Zheng <15...@users.noreply.github.com>
AuthorDate: Wed Jul 22 20:58:20 2026 -0700

    fix(BarChart): treat an empty categoryColumn as no category (px.bar color) (#6807)
    
    ### What changes were proposed in this PR?
    
    Fixes `BarChartOpDesc.generatePythonCode` treating an **unset**
    `categoryColumn` as a real column, which breaks `px.bar` at runtime.
    
    `categoryColumn`'s Scala field default is the empty string, while its
    JSON `defaultValue = "No Selection"` is only schema metadata (not
    applied to the Scala var, and not present when the field is absent from
    the deserialized JSON). The category guard compared **only** against
    `"No Selection"`:
    
    ```scala
    var isCategoryColumn = "False"
    if (categoryColumn != "No Selection")   // "" != "No Selection" is true
      isCategoryColumn = "True"
    ```
    
    So for an empty `categoryColumn`, `isCategoryColumn` became `"True"` and
    the empty column name flowed into the generated call:
    
    ```python
    color=self.decode_python_template('') if True else None   # -> px.bar(color="")
    ```
    
    `px.bar(color="")` raises at runtime, so a bar chart with **no category
    selected** fails.
    
    The fix also guards against empty, so an unset category yields
    `color=None`:
    
    ```diff
    -    if (categoryColumn != "No Selection")
    +    if (categoryColumn.nonEmpty && categoryColumn != "No Selection")
    ```
    
    ### Any related issues, documentation, discussions?
    
    Closes #6792
    
    ### How was this PR tested?
    
    Added a regression test in `BarChartOpDescSpec` that constructs a
    `BarChartOpDesc` with `value`/`fields` set and `categoryColumn` left at
    its default, calls `generatePythonCode()`, and asserts the color site is
    guarded to `None` (`... if False else None`) with no `... if True else
    None`. Verified the test **fails** on the pre-fix code and **passes**
    with the fix; full `BarChartOpDescSpec` is green (9/9).
    
    ### Was this PR authored or co-authored using generative AI tooling?
    
    Generated-by: Claude Code (Claude Opus 4.8)
    
    ---------
    
    Signed-off-by: Kary Zheng <15...@users.noreply.github.com>
    Co-authored-by: Claude Opus 4.8 <no...@anthropic.com>
    Co-authored-by: Copilot Autofix powered by AI <17...@users.noreply.github.com>
---
 .../amber/operator/visualization/barChart/BarChartOpDesc.scala |  4 +++-
 .../operator/visualization/barChart/BarChartOpDescSpec.scala   | 10 ++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDesc.scala b/common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDesc.scala
index 26ef772153..440437c9c0 100644
--- a/common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDesc.scala
+++ b/common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDesc.scala
@@ -109,7 +109,9 @@ class BarChartOpDesc extends PythonOperatorDescriptor {
       isPatternSelected = "True"
 
     var isCategoryColumn = "False"
-    if (categoryColumn != "No Selection")
+    // "" is the Scala default ("No Selection" is only JSON metadata); an empty
+    // column must also count as "no category", else px.bar(color="") fails.
+    if (categoryColumn.nonEmpty && categoryColumn != "No Selection")
       isCategoryColumn = "True"
 
     val finalCode =
diff --git a/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDescSpec.scala b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDescSpec.scala
index 3081b49d77..4c8afb0d36 100644
--- a/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDescSpec.scala
+++ b/common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/visualization/barChart/BarChartOpDescSpec.scala
@@ -110,4 +110,14 @@ class BarChartOpDescSpec extends AnyFlatSpec with BeforeAndAfter with Matchers {
     ex.getMessage should (include("Value column") or include("Fields"))
   }
 
+  "BarChartOpDesc.generatePythonCode" should "treat an unset categoryColumn as no category (color guarded to None)" in {
+    // An empty categoryColumn (its Scala default) must guard color to None, not
+    // emit `... if True else None` with an empty column name for px.bar(color=).
+    opDesc.value = "score"
+    opDesc.fields = "name"
+    val code = opDesc.generatePythonCode()
+    code should include("color=self.decode_python_template('') if False else None")
+    code should not include "color=self.decode_python_template('') if True else None"
+  }
+
 }