Fix missing spdx license expression in license detection

[alexzurbonsen]

Context

Occassionally, the spdx license expression is missing in license detections even though the license expression itself is non-null and a matching spdx expression would be available.

Should fix #4015

Summary

In the post processing step clues are converted to detections under certain conditions. This entails that their license expression may be updated if it was previously None. In these cases, we also need to update the spdx license expression.

It seems that this fix covers at least some instances of the bug, that I know of.

Test Plan

Run scancode on the example from #4015

scancode -l <path/to>/Amd.h  --json scancode_null_expression.json

The result:

"files": [
        {
            "path": "Amd.h",
            "type": "file",
            "detected_license_expression": "mpl-2.0",
            "detected_license_expression_spdx": "MPL-2.0",
            "license_detections": [
                {
                    "license_expression": "mpl-2.0",
                    "license_expression_spdx": "MPL-2.0",
                    "matches": [
                        {
                            "license_expression": "mpl-2.0",
                            "license_expression_spdx": "MPL-2.0",
                            "from_file": "Amd.h",
                            "start_line": 6,
                            "end_line": 8,
                            "matcher": "2-aho",
                            "score": 100.0,
                            "matched_length": 39,
                            "match_coverage": 100.0,
                            "rule_relevance": 100,
                            "rule_identifier": "mpl-2.0_3.RULE",
                            "rule_url": "https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/mpl-2.0_3.RULE"
                        }
                    ],
                    "identifier": "mpl_2_0-d0113b18-ff50-a2fd-17f7-9227082156a7"
                },
                {
                    "license_expression": "mpl-2.0",
                    "license_expression_spdx": "MPL-2.0",
                    "matches": [
                        {
                            "license_expression": "mpl-2.0",
                            "license_expression_spdx": "MPL-2.0",
                            "from_file": "Amd.h",
                            "start_line": 17,
                            "end_line": 18,
                            "matcher": "3-seq",
                            "score": 50.0,
                            "matched_length": 8,
                            "match_coverage": 50.0,
                            "rule_relevance": 100,
                            "rule_identifier": "mpl-2.0_97.RULE",
                            "rule_url": "https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/mpl-2.0_97.RULE"
                        }
                    ],
                    "identifier": "mpl_2_0-31c7f2f0-eb53-75b7-e843-a9ef4eb4ddf4"
                }
            ],
            "license_clues": [],
            "percentage_of_license_text": 2.27,
            "scan_errors": []
        }
    ]

scancode_null_expression.json

Tasks

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• Updated CHANGELOG.rst (if applicable)

[alexzurbonsen]

@AyanSinhaMahapatra Seems like this could fix #4015 ? It seems to work for the test file that I was looking at.