Error parsing parameter '--expression-attribute-values': Invalid JSON: Expecting property name enclosed in double quotes: line 1 column 3 (char 2)

Question

I am running the following query

aws dynamodb query `
--table-name user`
--key-condition-expression "datecreated = :d" `
--expression-attribute-values "{ ':d': { 'S': '2018-08-15' } }" --endpoint-url http://localhost:8000

Does dynamodb even understand what a double quote is?

1. I have tried swapping single quotes with double quotes.
2. Using double quotes everywhere
3. Doubling up the quotes, both single and double
4. Using slashes
5. Removing single quotes altogether

Answer 1

It's frustrating that this doesn't work more simply.

I have always double converted the object to json, like this:

$cliValue = $myObjectGraph | ConvertTo-Json -Depth 9 -Compress | ConvertTo-Json -Depth 9;

Which gives me $cliValue in this form:

"{\"ids\":[[\"94143814-c212-41b1-983f-e2d8ff589b2a\",\"My Description 1\"],[\"418a5f04-3d5a-4516-961f-6b0ab448edbb\",\"My Description 2\"], ...

Answer 2

There are two immediate problems:

• ' (single quotes) aren't valid string delimiters in JSON; you must use " (double quotes):

• Sadly, as of v7.2 PowerShell requires you to \-escape argument-internal " characters when calling external programs, even though that shouldn't be necessary.

  • See this answer for details, including a potential future (possibly opt-in) fix.
  • As an alternative to the manual \-escaping detailed below, you can use the PSv3+ ie helper function from the Native module (in PSv5+, install with Install-Module Native from the PowerShell Gallery), which internally compensates for all broken behavior and allows passing arguments as expected; to use it, simply prepend ie to your invocations; e.g.:
    ie aws dynamodb query ...

Therefore, try this; note how '...' is used for the outer quoting (which PowerShell transforms to double quotes behind the scenes) so that you needn't escape " as `" inside the string - do note that the string content is then treated literally;
The \-escaping, however, is always needed when calling an external program such as aws as of PowerShell 7.2:

... --expression-attribute-values '{ \":d\": { \"S\": \"2018-08-15\" } }'

---

If you do need "..." as the outer quoting in order to use string expansion (interpolation), i.e., in order to embed variable references and expressions, things get uglier, because you need to apply two kinds of escaping: `" first, to satisfy PowerShell's syntax requirements, preceded by \ to ensure the resulting embedded " are correctly passed through to the target program:

$date = [datetime]::now.ToString('yyyy-MM-dd')
... --expression-attribute-values "{ \`":d\`": { \`"S\`": \`"$date\`" } }"

---

A here-string can ease the pain, but note that it invariably makes the command multi-line - and the need for \-escaping still applies (note that "@, the closing delimiter must not only be on its own line, it must be at the very start of that line):

... --expression-attribute-values @"
  { \":d\": { \"S\": \"$date\" } }
"@

Answer 3

I encountered this problem when I wanted to create a bash script that accept an argument so that I can make a query with various input.

One way to avoid the problem was to use temporary json file.

In bash script:

attrvalues="{\":d\": {\"S\": \"$1\"}}"
echo "$attrvalues" > attr-values.json

which would create a file below if you provide 2021-01-31 as first input:

{
  ":d": {"S": "2021-01-31"}
}

Then in bash script:

aws dynamodb query \
    --table-name user \
    --key-condition-expression "datecreated = :d" \
    --expression-attribute-values file://attr-values.json \
    --endpoint-url http://localhost:8000

rm attr-values.json

Answer 4

I've gone through the same issue just now when using Key-Condition-Expression Parameter

aws dynamodb query --table-name mystore --key-condition-expression "clientid = :name" --expression-attribute-values '{":name":{"S":"chris@example.com"}}'

which would give

In order to solve it, just had to change the command to (note the \")

aws dynamodb query --table-name mystore --key-condition-expression "clientid = :name" --expression-attribute-values '{\":name\":{\"S\":\"chris@example.com\"}}'