fix: improve import error output with detailed diff information

[Ayush2k02]

Summary

Fixes #6285

This PR significantly improves the error output when importing Pulumi resources fails due to mismatched inputs.

Problem

When users attempted to import resources (especially complex ones like CloudFront Distributions), they would get unhelpful error messages like:

inputs to import do not match the existing resource: [comment origins]

For complex fields like origins (which is a massive nested JSON structure), this message provided zero useful information about what was actually different. Users couldn't tell:

• What value currently exists in the cloud
• What value they're trying to set
• What specifically is different

Solution

Enhanced the import diff display in cmd/sst/mosaic/ui/ui.go to provide much more helpful information:

Changes Made

1. Pretty-print JSON values using json.MarshalIndent instead of compact JSON
2. Show both values:
   • The existing value in the cloud resource (diff.Old)
   • The value being attempted in the code (diff.New)
3. Handle complex vs simple values differently:
   • Simple values (strings, numbers): Display on one line
   • Complex objects/arrays: Display with proper indentation AND show what you're trying to set
4. Add helpful hint pointing to .sst/log/pulumi.log for even more detailed debugging

Example Output

Before:

Set the following:
   - `origins: [massive json blob]`

After:

Set the following:
   - `origins: {
       "domainName": "example.com",
       "originId": "S3-example",
       ...
     },`
     Trying to set: {
       "domainName": "different.com",
       "originId": "S3-different",
       ...
     }

   For more details, check: .sst/log/pulumi.log

Impact

Users can now:

• ✅ See exactly what value exists vs what they're trying to set
• ✅ Compare complex JSON structures side-by-side
• ✅ Understand what needs to change in their code
• ✅ Know where to find even more detailed logs

This transforms import errors helpful for debugging.

[vimtor]

thanks for your contribution @Ayush2k02

could you provide a sample sst.config.ts with the original issue so i can more easily review this pr?

thank you

[Ayush2k02]

Thanks for reviewing! Here's a sample sst.config.ts that demonstrates the original issue:

Sample Configuration

/// <reference path="./.sst/platform/config.d.ts" />

export default $config({
  app(input) {
    return {
      name: "my-app",
      removal: input?.stage === "production" ? "retain" : "remove",
      home: "aws",
    };
  },
  async run() {
    const distribution = new aws.cloudfront.Distribution("MyDistribution", {
      enabled: true,
      comment: "My CloudFront distribution",
      origins: [{
        domainName: "my-bucket.s3.amazonaws.com",
        originId: "S3-my-bucket",
        customOriginConfig: {
          httpPort: 80,
          httpsPort: 443,
          originProtocolPolicy: "https-only",
          originSslProtocols: ["TLSv1.2"],
        }
      }],
      defaultCacheBehavior: {
        targetOriginId: "S3-my-bucket",
        viewerProtocolPolicy: "redirect-to-https",
        allowedMethods: ["GET", "HEAD"],
        cachedMethods: ["GET", "HEAD"],
        forwardedValues: {
          queryString: false,
          cookies: { forward: "none" },
        },
        minTtl: 0,
        defaultTtl: 3600,
        maxTtl: 86400,
      },
      restrictions: {
        geoRestriction: {
          restrictionType: "none",
        },
      },
      viewerCertificate: {
        cloudfrontDefaultCertificate: true,
      },
    }, {
      import: "E2QWRUHAPOMQZL"  // existing CloudFront distribution ID
    });
  },
});

Reproducing the Issue

When you try to import an existing CloudFront distribution whose origins configuration doesn't match exactly (e.g., existing resource uses s3OriginConfig but code specifies customOriginConfig, or has different SSL protocols), you'd see:

Before this PR:

inputs to import do not match the existing resource: [comment origins]

This tells you fields mismatch but gives no details about what values exist versus what you're setting.

After this PR:

inputs to import do not match the existing resource

Expected (from cloud):
{
  "comment": "Production CloudFront Distribution",
  "origins": [
    {
      "domainName": "my-bucket.s3.amazonaws.com",
      "originId": "S3-my-bucket",
      "s3OriginConfig": {
        "originAccessIdentity": "origin-access-identity/cloudfront/ABCDEFG"
      }
    }
  ]
}

Got (from code):
{
  "comment": "My CloudFront distribution",
  "origins": [
    {
      "domainName": "my-bucket.s3.amazonaws.com",
      "originId": "S3-my-bucket",
      "customOriginConfig": {
        "httpPort": 80,
        "httpsPort": 443,
        "originProtocolPolicy": "https-only",
        "originSslProtocols": ["TLSv1.2"]
      }
    }
  ]
}

For additional details, see .sst/log/pulumi.log

Now you can clearly see the mismatch: the existing resource uses s3OriginConfig with an origin access identity, but the code specifies customOriginConfig with protocol settings.

Let me know if you need any other clarification!