Add support for using get if resource doesn't implement export

Author: SteveL-MSFT

dsc/tests/dsc_export.tests.ps1

@@ -181,4 +181,42 @@ resources:
         $out.resources[0].properties.psobject.properties.name | Should -Not -Contain '_securityContext'
         $out.resources[0].properties.psobject.properties.name | Should -Not -Contain '_name'
     }
+
+    It 'Export can be used with a resource that only implements Get with filter' {
+      $yaml = @'
+$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
+resources:
+  - name: NoExport
+    type: Test/Get
+    properties:
+      name: two
+'@
+      $out = dsc config export -i $yaml | ConvertFrom-Json
+      $LASTEXITCODE | Should -Be 0
+      $out.resources.count | Should -Be 1
+      $out.resources[0].type | Should -BeExactly 'Test/Get'
+      $out.resources[0].properties.name | Should -BeExactly 'two'
+      $out.resources[0].properties.id | Should -Be 2
+    }
+
+    It 'Export can be used with a resource that only implements Get with no filter' {
+      $yaml = @'
+$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
+resources:
+  - name: OS
+    type: Microsoft/OSInfo
+'@
+      $out = dsc config export -i $yaml | ConvertFrom-Json
+      $LASTEXITCODE | Should -Be 0
+      $out.resources.count | Should -Be 1
+      $out.resources[0].type | Should -BeExactly 'Microsoft/OSInfo'
+      $expectedOs = if ($IsWindows) {
+          'Windows'
+      } elseif ($IsMacOS) {
+          'macOS'
+      } else {
+          'Linux'
+      }
+      $out.resources[0].properties.family | Should -BeExactly $expectedOs
+    }
 }

dsc_lib/src/dscresources/command_resource.rs

@@ -487,6 +487,26 @@ pub fn get_schema(resource: &ResourceManifest, cwd: &str) -> Result<String, DscE
 /// Error returned if the resource does not successfully export the current state
 pub fn invoke_export(resource: &ResourceManifest, cwd: &str, input: Option<&str>) -> Result<ExportResult, DscError> {
     let Some(export) = resource.export.as_ref() else {
+        // see if get is supported and use that instead
+        if resource.get.is_some() {
+            info!("{}", t!("dscresources.commandResource.exportNotSupportedUsingGet", resource = &resource.resource_type));
+            let get_result = invoke_get(resource, cwd, input.unwrap_or(""))?;
+            let mut instances: Vec<Value> = Vec::new();
+            match get_result {
+                GetResult::Group(group_response) => {
+                    for result in group_response {
+                        instances.push(serde_json::to_value(result)?);
+                    }
+                },
+                GetResult::Resource(response) => {
+                    instances.push(response.actual_state);
+                }
+            }
+            return Ok(ExportResult {
+                actual_state: instances,
+            });
+        }
+        // if neither export nor get is supported, return an error
         return Err(DscError::Operation(t!("dscresources.commandResource.exportNotSupported", resource = &resource.resource_type).to_string()))
     };
 
@@ -840,7 +860,7 @@ fn json_to_hashmap(json: &str) -> Result<HashMap<String, String>, DscError> {
                 },
                 Value::Null => {
                     // ignore null values
-                },  
+                },
                 Value::Object(_) => {
                     return Err(DscError::Operation(t!("dscresources.commandResource.invalidKey", key = key).to_string()));
                 },

tools/dsctest/dscget.dsc.resource.json

@@ -0,0 +1,25 @@
+{
+    "$schema": "https://aka.ms/dsc/schemas/v3/bundled/resource/manifest.json",
+    "type": "Test/Get",
+    "version": "0.1.0",
+    "get": {
+        "executable": "dsctest",
+        "args": [
+            "get",
+            {
+                "jsonInputArg": "--input",
+                "mandatory": true
+            }
+        ]
+    },
+    "schema": {
+        "command": {
+            "executable": "dsctest",
+            "args": [
+                "schema",
+                "-s",
+                "get"
+            ]
+        }
+    }
+}

tools/dsctest/src/args.rs

@@ -10,6 +10,7 @@ pub enum Schemas {
     ExitCode,
     Export,
     Exporter,
+    Get,
     InDesiredState,
     Metadata,
     Sleep,
@@ -57,6 +58,12 @@ pub enum SubCommand {
         input: String,
     },
 
+    #[clap(name = "get", about = "Get a resource")]
+    Get {
+        #[clap(name = "input", short, long, help = "The input to the get command as JSON")]
+        input: String,
+    },
+
     #[clap(name = "in-desired-state", about = "Specify if the resource is in the desired state")]
     InDesiredState {
         #[clap(name = "input", short, long, help = "The input to the in desired state command as JSON")]

tools/dsctest/src/get.rs

@@ -0,0 +1,12 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct Get {
+    pub name: Option<String>,
+    pub id: Option<i32>,
+}

tools/dsctest/src/main.rs

@@ -7,6 +7,7 @@ mod exist;
 mod exit_code;
 mod export;
 mod exporter;
+mod get;
 mod in_desired_state;
 mod metadata;
 mod sleep;
@@ -22,6 +23,7 @@ use crate::exist::{Exist, State};
 use crate::exit_code::ExitCode;
 use crate::export::Export;
 use crate::exporter::{Exporter, Resource};
+use crate::get::Get;
 use crate::in_desired_state::InDesiredState;
 use crate::metadata::Metadata;
 use crate::sleep::Sleep;
@@ -113,6 +115,45 @@ fn main() {
             }
             String::new()
         },
+        SubCommand::Get { input } => {
+            let get = match serde_json::from_str::<Get>(&input) {
+                Ok(get) => get,
+                Err(err) => {
+                    eprintln!("Error JSON does not match schema: {err}");
+                    std::process::exit(1);
+                }
+            };
+            let instances = vec![
+                Get {
+                    name : Some("one".to_string()),
+                    id: Some(1),
+                },
+                Get {
+                    name : Some("two".to_string()),
+                    id: Some(2),
+                },
+                Get {
+                    name : Some("three".to_string()),
+                    id: Some(3),
+                },
+            ];
+            // depending on the input, return the appropriate instance whether it is name or id or both
+            let resource = if let Some(name) = get.name {
+                instances.into_iter().find(|i| i.name == Some(name.clone())).unwrap_or_else(|| {
+                    eprintln!("No instance found with name: {}", name);
+                    std::process::exit(1);
+                })
+            } else if let Some(id) = get.id {
+                instances.into_iter().find(|i| i.id == Some(id)).unwrap_or_else(|| {
+                    eprintln!("No instance found with id: {}", id);
+                    std::process::exit(1);
+                })
+            } else {
+                eprintln!("No name or id provided in input");
+                std::process::exit(1);
+            };
+            serde_json::to_string(&resource).unwrap()
+        },
         SubCommand::InDesiredState { input } => {
             let mut in_desired_state = match serde_json::from_str::<in_desired_state::InDesiredState>(&input) {
                 Ok(in_desired_state) => in_desired_state,
@@ -162,6 +203,9 @@ fn main() {
                 Schemas::Exporter => {
                     schema_for!(Exporter)
                 },
+                Schemas::Get => {
+                    schema_for!(Get)
+                },
                 Schemas::InDesiredState => {
                     schema_for!(InDesiredState)
                 },