DataFlex

Impossible Execution Plan

See more CURL Examples

This example demonstrates what happens when it is not possible to construct an execution plan due to missing dependencies.

The target curl command requires a {{drive_id}} value. However, no variable named drive_id has been defined, and no helper function is registered that can produce it. Although a helper function (getSite) is defined, it only produces site_id, which does not satisfy the requirement.

When ExaminePlan is called, it reports that the execution plan cannot be created because a required input is missing and no function exists to provide it.

When DoYourThing is called, it fails for the same reason. The failure is not due to a network or HTTP error, but because the dependency graph cannot be resolved. The FailReason property indicates this condition with a specific error code.

This example highlights that for an execution plan to be valid, every required input must either:

• Already have a defined value, or
• Be producible by a defined curl function with resolvable inputs

If neither condition is met, the system correctly detects the unresolved dependency and prevents execution.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoHttpCurl
    String sTargetCurl
    String sFnName
    String sJsonPath
    Variant vJsonOAuth2
    Handle hoJsonOAuth2
    Integer iStatusCode
    Variant vResponseJson
    Handle hoResponseJson
    String sTemp1

    Move False To iSuccess

    Get Create (RefClass(cComChilkatHttpCurl)) To hoHttpCurl
    If (Not(IsComObjectCreated(hoHttpCurl))) Begin
        Send CreateComObject of hoHttpCurl
    End

    // The final curl command we want to execute.
    // It depends on {{drive_id}}, which is not yet known.
    Move "curl -X GET https://graph.microsoft.com/v1.0/drives/{{drive_id}}/root/children" To sTargetCurl

    // Define a helper function that can produce drive_id.
    // This function lists drives for a given site, which requires {{site_id}}.
    Move "getDrives" To sFnName
    Get ComAddFunction Of hoHttpCurl sFnName "curl -X GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives" To iSuccess

    // Define the output of getDrives.
    // The JSON response contains an array named "value".
    // We take the first element (value[0]) and extract its "id" as drive_id.
    Move "value[0].id" To sJsonPath
    Get ComAddOutput Of hoHttpCurl sFnName sJsonPath "drive_id" To iSuccess

    // drive_id depends on site_id, which is also not yet known.
    // Define another helper function to obtain site_id.
    Move "getSite" To sFnName
    Get ComAddFunction Of hoHttpCurl sFnName "GET https://graph.microsoft.com/v1.0/sites/root:/sites/{{site_name}}" To iSuccess

    // Map the "id" field from the getSite response to the variable site_id.
    Move "id" To sJsonPath
    Get ComAddOutput Of hoHttpCurl sFnName sJsonPath "site_id" To iSuccess

    // Provide the initial known input.
    // site_name is the starting value that allows the dependency chain to be resolved.
    Send ComSetVar To hoHttpCurl "site_name" "test"

    // ----------------------------------------------------------------------------------------------------------------------
    // Configure OAuth2 authentication using the client credentials flow.
    // Secrets (client_id, client_secret, token_endpoint) are retrieved from the
    // local secrets manager because EnableSecrets is enabled.
    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonOAuth2
    If (Not(IsComObjectCreated(hoJsonOAuth2))) Begin
        Send CreateComObject of hoJsonOAuth2
    End
    Set ComEnableSecrets Of hoJsonOAuth2 To True
    Get ComUpdateString Of hoJsonOAuth2 "oauth2.client_id" "!!sharepoint|oauth2|client_id" To iSuccess
    Get ComUpdateString Of hoJsonOAuth2 "oauth2.client_secret" "!!sharepoint|oauth2|client_secret" To iSuccess
    Get ComUpdateString Of hoJsonOAuth2 "oauth2.scope" "https://graph.microsoft.com/.default" To iSuccess
    Get ComUpdateString Of hoJsonOAuth2 "oauth2.token_endpoint" "!!sharepoint|oauth2|token_endpoint" To iSuccess
    Get pvComObject of hoJsonOAuth2 to vJsonOAuth2
    Get ComSetAuth Of hoHttpCurl vJsonOAuth2 To iSuccess
    // ----------------------------------------------------------------------------------------------------------------------

    // Execute the target curl command.
    // Internally, the system will:
    // 
    // 1) Detect that {{drive_id}} is required but not defined.
    // 2) Find that "getDrives" can produce drive_id.
    // 3) Detect that getDrives requires {{site_id}}, which is also not defined.
    // 4) Find that "getSite" can produce site_id.
    // 5) Verify that getSite requires {{site_name}}, which is already known.
    // 6) Build a multi-step execution plan:
    //      - First:  run getSite (produces site_id)
    //      - Second: run getDrives (produces drive_id)
    //      - Third:  run the target curl (uses drive_id)
    Get ComDoYourThing Of hoHttpCurl sTargetCurl To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoHttpCurl To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Retrieve and display the HTTP response status code.
    Get ComStatusCode Of hoHttpCurl To iStatusCode
    Showln "response status code: " iStatusCode

    // Load and display the JSON response from the final curl command.
    Get Create (RefClass(cComChilkatJsonObject)) To hoResponseJson
    If (Not(IsComObjectCreated(hoResponseJson))) Begin
        Send CreateComObject of hoResponseJson
    End
    Set ComEmitCompact Of hoResponseJson To False
    Get pvComObject of hoResponseJson to vResponseJson
    Get ComGetResponseJson Of hoHttpCurl vResponseJson To iSuccess
    Get ComEmit Of hoResponseJson To sTemp1
    Showln sTemp1


End_Procedure