Can't replace shadow blocks in statement inputs

[maribethb]

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Description

Shadow blocks connected to statement inputs can't be replaced. When dragging a new block, there is no insertion marker and the blocks are not connected when you release the drag. If there is no shadow block, things work fine.

Shadow blocks work fine when connected to value inputs.

Note this is new in 9.3.0

Related: https://groups.google.com/g/blockly/c/r3Jw5uhHvuc

Reproduction steps

1. Open the Code demo
2. Paste the following into the JSON tab
3. Try to drag a new print block into the statement connection, observe no connection is made

{
  "blocks": {
    "languageVersion": 0,
    "blocks": [
      {
        "type": "controls_repeat_ext",
        "id": "K[j){YWz}cgy~}L]bY~!",
        "x": 237,
        "y": 138,
        "inputs": {
          "TIMES": {
            "shadow": {
              "type": "math_number",
              "id": "Y@%oW+58GnOknRlkKsUi",
              "fields": {
                "NUM": 10
              }
            }
          },
          "DO": {
            "shadow": {
              "type": "text_print",
              "id": "lk}*,J0qTdg@8Eu7767Y",
              "inputs": {
                "TEXT": {
                  "shadow": {
                    "type": "text",
                    "id": "9UPY%/4+oy{*T#dxp_D`",
                    "fields": {
                      "TEXT": "abc"
                    }
                  }
                }
              }
            }
          }
        }
      },
      {
        "type": "text_print",
        "id": "Wx=@]t{O2#[xcgC%n6kl",
        "x": 363,
        "y": 287,
        "inputs": {
          "TEXT": {
            "shadow": {
              "type": "text",
              "id": "RgRfIE##~8SO?kV7!BRP",
              "fields": {
                "TEXT": "abc"
              }
            }
          }
        }
      }
    ]
  }
}

Stack trace

No errors or messages.

Screenshots

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Browsers

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[maribethb]

Update: We are working on fixing this issue and will release a patch. The root cause is #6800